^exactly. The middle is a very painful place, whilst middle for me means (in PvE) starting/farming T5 content. There is a huge impact of the gear shop considering how the attunements work in TBC. Also, if you plan to start PvE, be very mindful with your guild, due to all of the above mentioned, and for being a far slower version of the game as it is today, a lot of players quit after being 70 for a few weeks so that you (my personal xp) constantly need to refill your roster if you want to progress in raids which need Champion or higher attunements.
After playing on both Iecrown and Outland, I would always prefer Outland because everything you do feels a lot more rewarding due to the more RPG and "slow-but-worthwile" oriented focus of the game. This is (all imo) a perfectly made TBC server with the one exception that being able to buy key items from high tier content has a far higher and far more toxic impact on this type of game style than it could possibly have on WotLK.
If you want to play PvP seriously you almost have to buy, because most PvP Players today (I believe) do not want to and most likely will not farm and raid for 3-4 months before starting to feel some kind of competition in arenas. Generalization never works well but it is like you always encounter the exact same gear setup on, for example, rogues, which is usually just the best you can buy via donation, which would cost you, ofc depending on effort and luck, at least 3 month worth of farming/raiding. It is a different story if you are, as a PvP player, fine with lets say getting totally stomped for at least a week of playtime whilst waiting countless weeks for arena point flushing.
But by all means, if you are interested in the style of TBC and/or Vanilla, go ahead because these two where definitely the best World of Warcraft experience and by far the best MMORPG experience of all times - or do you know somebody who quit his job/abandoned his marriage etc. for WotLK, Cata, MoP, WoD or Legion? Maybe you srsly do but even so, there are plenty of skilled mechanics and **** and the overall skilllevel of players is tremendously higher than back in the days but you won't ever get totally sucked into Azeroth again after the end of TBC (afaik :D).
Just have fun and do what ever you might enjoy more.