I would think the way to go with a pressurized tank would be to charge the tank with whatever temp you want, Slow the flow down so you only run the water through one time.(or less if not fully charged). Less electric and a tank of unmixed water. This may also be one of the most efficient setups if the bottom temp is 140 or less.
Theory may be good but doesn't work in the real gasser world. The gasser wants and needs to operate at high burn until the load is exhausted. If you slow the flow down too much, the gasser will produce more btu's than you are using, boiler water temp will rise, and the gasser will idle at somewhere around 185-190F. IMO the goal is to get all the btu's the gasser is producing out into the zones or storage to prevent any idling. This flow rate will depend upon the delta-T. At below 140 system return, there will or should be some boiler return water protection mixing occurring to keep boiler return at 140 minimum (some say should be as high as 160). So the flow has to be sufficient to provide the required mixing plus take the btu's to system/storage to keep the boiler from moving into idle. This is pretty easy with low system return. Example: 140F system return, 180F boiler output, delta-T = 40, gpm to system only has to be 5 to handle up to 100,000 btu's. Keep in mind that in this example some gpm's and btu's are being used for boiler return water protection. A 15-58 on L likely will do this, depending on system head.
But as delta-T closes, it can get much more difficult. If system return is 160F or higher, no boiler return water protection is needed. If boiler output is 180F, delta-T = 20, now 10 gpm's to system are needed to move 100,000 btu's, and since no gpm's or btu's are being used for return water protection, you likely need more than 10 gpm's on a 140,000 btu rated boiler to prevent boiler temp from rising and the boiler going into idle. A system which handles 5 gpm's will see about a 3x increase in pump head as gpm's move to 10 gpm's. Depending on system design, it may take lots of circ power to achieve this.
So, once you calculate needed circ flow rate, you also need to calculate pump head at that flow rate, and then select a circ that can deliver the required flow at the calculated head. Simply increasing circ speed on a variable speed circ may not be enough. One person may have 1.25" lines and storage located right next to the boiler, maybe 50 feet equivalent pipe length. Another may have storage and boiler located quite a distance apart, and maybe 1.0" lines. There will be a radical difference in circ and speed selection in these two circumstances.
Not to be forgotten in this mix is flue temp. Although the gasser needs to operate at high burn, beginning to end, you do have some, or maybe a lot, of control over flue temp, and boiler btu output, by adjusting the draft fan damper/control. Full draft on high burn may produce flue temps of 600F and higher for some, which also means higher btu output; but slowing the draft down for a flue temp of 400-500F (some may go less) also results in lower btu output. Therefore, I think you also have to consider your target flue temp on high burn. My Tarm on very dry aspen/pine mix typically operates 400-600F flue temp over a burn with my current fixed draft damper adjustment, which is closed a moderate amount. If the draft damper was wide open I would see flue temps of 700F and for a short time even higher during highest burn periods.
The theory of this discussion is good for everyone interested, but the application will vary widely depending on the circumstances of each installation.
Some other thoughts. If system return is 140F or lower, until boiler temp gets up to at least 160F (maybe higher) at the boiler output port based on gravity heating inside the boiler, I don't see any need to operate the primary circ at all. Any operation below 160F will mostly recirculate boiler water through boiler return water protection. Nofo says he provides some system circulation so the boiler won't see a shock of cold water. This probably makes sense as he uses bang bang return water boiler protection. I don't see that need with the Termovar (or similar), as any cold water shock seems to be extremely brief, the Termovar rapidly limiting output to system and mixing to achieve 140+F return water protection.
As to artificially increasing flow resistance, I agree with Goose, the exception being to provide required boiler return water protection.
As to flow rate and impact on stratification in storage. This is subject to lots of variables, depending on each installation. For me, I have flow rates of about 2 gpm minimum (system return below 120F and boiler output 160-165F) and up to about 10 gpm on the high side. The 2 gpm is not surprising, as 2 gpm = 100,000 btu at bottom of tank 70F and boiler output 170F. The higher flow rates occur as bottom of tank temps (return to system) gets above about 160F. Flow rates increase "automatically" over this range as the Termovar increasingly opens to provide less boiler return water protection. I see very little impact on stratification in my storage tank over this flow range, and at the high end it also doesn't matter much. If bottom of tank is 160+F, top of tank input is going to be 175-195F, and at 10 gpm (600 gph), mixing the tank up to 180-190F will occur nearly as fast as trying to continue to stratify as the tank heats up to 180-190F.
In addition to the "automatic" increase in flow rates, I have a 007 in series with the 15-58. The 007 is triggered by a separate aquastat, and I currently turn on the 007 when boiler output hits 185F. This gives the gpm boost I need to handle the btu's and keep the boler from going into idle. The 007 cycles on and off as needed over a burn and does a very good job at limiting any idling. Currently, I experience idling only as bottom of tank return to boiler is about 170F +/-, meaning a delta-T of 20 or less. Since my maximum flow is about 10 gpm, delta-T = 20 = 100,000 btu, which is less than the Tarm puts out, depending on the stage of the burn. I usually do not charge storage to above 160F at bottom of tank. Top of tank will be 180-190F in this circumstance.