Like most people here, I have a sizable collection of tripods. My thoughts on the features you mentioned:
- Lever vs. twist locks: My preference is definitely levers. They are quicker to open and close, no chance of accidentally unscrewing them too far and losing a shim, or tightening too hard and breaking a shim. However the more compact you get, the more likely you will be locked into twist locks.
- QR plate: For quick operation, I love Manfrotto's RC2 system. Arca plates are pretty standard across all brands, but you have to slide it to the right position and tighten a thumb screw to lock it in place - not really quick. With RC2, it just snaps in and you push down a clamp.
- Size: I tend to group tripods into 3 size categories, full size, travel, and compact. Full-size is typically big and heavy, very stable, and not good for travel. Travel tripods make some compromises, but tend to be very usable, and typically get strapped to the outside of your camera bag. Compact folds down to 12-15", and is made to fit inside of luggage and sometimes even inside of camera bags, but obviously come with some compromises in stability, max load, and height.
For a full-sized, tripod, Manfrotto's 055 or 190 aluminum tripods with a decent ball head are fantastic. You're probably not going to travel too much with these, so I don't think it's worth the cost to go with carbon fiber, since the whole point is to be big and heavy. I have an 055XProB with an 054 head that come in at 6.5lbs - solid performer as long as I don't have to walk far.
For a mid-sized travel tripod, my choice is the
Aluminum Manfrotto BeFree Advanced with lever locks. On paper, the specs look almost as good as a heavier full-sized version, you get the RC2 QR plate and lever locks, and a very stable platform in a 3.6lb package. I think this or one of the other similar BeFree models might fit your needs, and a good compromise between size and weight while still getting good stability.
For something compact, my go-to tripod is now a Sirui T-025SK, which folds down to about 12", fits inside my camera bag, and can still hold the weight of a full-sized SLR with a big lens. I don't know if this will be stable enough for your needs, but I have a thread about it
here if you want to read my review.
Good luck with your growing tripod collection!