For an insert, do you really need a liner in an existing masonary chimney without cracks?

I'm sure this has been posted on here somewhere. Just curious since I've read some posts that people have put in "I believe there are three different kinds of tubing". They also insulate it somehow. What is the point in insulating around your tube inside the masonry brick chimney?

They also put a cap on the flues top. Does this greatly benefit those with cats? If I already have plenty of draft. Does it make your stove more efficient or is it unnecessary if you have plenty of draft already? I'd hate to have to blow another 500 or whatever it costs for more labor and materials on an already expensive stove.

I don't know anything about a clay liner. The house is from the early to mid 50's. The fireplace brick goes from wall to wall upstairs living room and downstairs around 15 feet wide. All I know is we've been using an old bk since the early 80s and has plenty, if not too much draft. It's downstairs, so the chimney is around 22 feet tall. Never really worried about a chimney fire, since we have went 8-10 years without cleaning and a around 3 chords a year. lol. I'm thinking the wasted wood of super hot fires burned it off, or kept it from getting too dirty. Just got it cleaned last year, and didn't use it much. I need to seal around it better, since once it gets going, you cant really stop it or slow it down enough, and lumber scraps burn too hot and fast. I've been scared before, when I couldn't slow it down and the top and metal door were glowing red. Thought it may melt, lol. I just turned the jet air on high, and it would burn up the wood within an hour or so. Maybe I need to seal around it better with sealant.

It's an exterior fireplace. Glass screen firebox old school up stairs for small fires to look at, and downstairs is the insert=for actual heat. I don't have control over the chimney damper with the insert in it, as it's located inside. "no handle coming out of the brick". Even when the air entrance on the stove is closed, I can still see gaps of light from the fire on the sides. Inlet is like 2 inches by 4 or 5 inches wide. It just goes through too much wood, with the lack of being able to control it well, and is time to part, even with all the sentimental value to me.

I think the cap might improve draft as well, or prevent downdrafts, but the top plate and cap seal your chimney so that rain doesn't run down inside your masonry chimney where it can freeze and thaw, damaging the clay liner or brick. You also don't want water inside your stove. My cap has a mesh screen that would keep large pieces of burning creosote contained in case of a chimney fire. The stainless parts aren't cheap. Do it right, once, and you're done. I went with the best liner and hardware I could get...got a little under $1000 up there, including liner, tee, top plate, clamp, cap and insulation. I now have peace of mind and a great-performing system. You might be able to do it with a cheaper, thinner liner for $500+ if you install it yourself, like I did. You might be able to forego the insulation if you have an interior chimney, but it would be better to insulate too...

Be green, I have a clay lined exterior double brick chimney that the installer put a stainless liner into when I got my new stove installed. I am wondering if I should pour some perlite insulation down from the top of the chimney to help insulate. Do you think this is a good idea to help keep the liner cleaner? Sorry if I posted this in the wrong place. I have done a quick search of the site for this but could not get an answer.
Thanks

My chimney is outside/attached to the house and is around 20ft high. It draws well and have no prob with puffing or backing issues. My main concern is creosote buildup as I sometimes hear some falling down the chimney on startup from cold. Not a lot but enough that i will clean the chimney shortly, I am just getting used to burning the stove and was not burning hot enough so have remedied that by starting with stovetop 500 600f before closing air down in increments.

If someone is running in an open clay liner, i dont se a problem running an uninsulated liner down the same chimney regardless of where it is on the home. If there cleaning it running dry wood and getting it up to temp they will have no more creosote problem than what they were doing before. Not optimal but in my UNEXPERT opinion is not worse than how they are now.

Years ago, the manufacturer of the stainless liner we were using at the time sent out a warning about loose-pour insulation (vermiculite, zonolite, perlite). They claimed the loose pour created tiny "hot spots" where the individual pellets actually came in contact with the liner, each surrounded by a cooler "doughnut" created by the airspace between the pellets. This, they claimed, caused some of the components of the stainless to flee the hot spots and migrate into the cooler perimeters (a process they called "nickling"), which weakened the liner. They further announced that use of loose-pour insulation would void their 25-year liner warranty. Their recommendation was a tight-sealing top plate to create dead-air insulation. For situations where solid insulation was required, they recommended wet-pour (slurry) or blanket insulation.