What do you prefer and what size?

Pads, and very thick reedy and grassy vegetation.....braid 65lb

Timber....25lb fluoro (but I usually just end up using braid to 17lb CXX leader because I hate babysitting fluoro)

Anyone use mono for this technique?

65lb braid with a 20lb invisX fluoro carbon leader. If you use a leader on braid you need to back the drag off a little to keep from breaking the leader on hook sets.

It's all I use... Braid is over kill and floro is a pain with it's memory... Trilene XL is all I use... Dan

If I am flipping/pitching (and sometimes frogging) in structure and/or heavy cover I occasionally use braid with a mono leader. For the braid I typically go with 40#. Its abrasion resistant enough to last, strong enough for any fish and usually I can drag back a wad of grass, pads or whatever. On the leader, I keep it short - around 20" and no more than 25" and will use 17-20# depending on the brand. The mono helps give me the "rubber band" effect for good sensitivity and effective hook-sets. If I break off the leader due to a snag I'm not going to cry over the jig/lure/bait. The braid is a pain if it is tangled underneath. You have to manipulate the boat over to it and either get it loose or cut it close to the water. If you can get the leader to break the slingshot effect will sometimes free the braid. I have a rod/reel set up for this scenario but frankly, I use it on a rare occasion where the under water conditions are pretty bad. Most of the time I'll use 20# mono and maybe a lighter weight mono leader for the same situation where a few snags are tolerable and I have time to deal with them. Using either set-up I have the same fish-in-the-boat count. Maybe we could be more informative if you are more specific about why you're asking and what you're trying to accomplish.

Thanks everyone.
Bar, I am getting a Tatula Elite PF reel and putting it on a 7'3" H flipping rod. The areas I fish mostly would be laydowns, rocks, maybe some cattails. Probably almost never pads or mats unless I am traveling somewhere. Want kind of a do-it all setup as far as pitching so it will be used with jigs and t-rig plastics.

I will use braid (65) only when necessary. Everything else I use fluorocarbon. Test depends on the water I am fishing. I go anywhere from 15-20 usually. With what you listed I would use fluoro except for cattails.

Trilene XT for me unless I'm in some super thick stuff.

Yes sir

From one of the best;

https://bassblaster.rocks/greg-hackneys-braid-flipping-system

That will be a good combo. Also check out the 2020 version of the Tatula SV TW. I use it for skipping docks because of the advanced cast control this reel has to keep from backlashing. It sells for around $199.

Sunline Sniper in 12, 16, and 20# depending on cover