which version of thaumcraft do you recommend playing?

if you want the raw experience, thaumcraft 4 id say .

its the most balanced and well loved version of the mod and works well . itll show you thaumcraft at its best and usually rawest form, with imo the best research mechanic in the series by far as well as the balancing for aspects in items. and theres functional pipework (unlike tc6) which can be finnicky but once you get the hang of it all it can be quite fun :)

i recommend add-ons like thaumic horizons and thaumic tinkerer, theres a lot more good add ons for tc4 that you definitely should try out if you like jumping head into such things

if you cant stand the older minecraft version though you can always play thaumcraft 6 but you should ABSOLUTELY get thaumic augmentations on that one because tc6 is unfinished and that add on finishes the end game content nicely . tc6 is actually the first version ive experienced lol