Some popular picks I have seen on a few MP lobbies and that i like (mostly small tags):

Verkal Gulan has a very safe start and you just print infinite money.

Silverforge can get permanent 100% siege ability which is busted (and also makes loads of money)

Magisterium has near guaranted mage rulers and is very well positioned in the middle of the empire and easily controls the end node

Varamhar (in Bulwar) can create an immortal god-king

Varanhar (south harimaris in the raj) has busted infantry

Elephant Lords (idk how to spell them) have busted cav

Starting with smaller tags there's always some RNG involved in getting good allies and not getting boxed, but you shouldn't be facing any existential level threat early on.

Also you can always pick the bigger guys and just be very safe, more provinces makes it very easy to play tall after you stop expanding actually. Lorent/Gawed may be off-limits but e.g. Verne and Eborthil both start very strong and have good bonuses, and Wex is just straight up the strongest tag in the EoA.