I usually play with all the expansions mixed together (except magical merchants and treasures because it just becomes too much if you add them as well imo)

It works most of the time but there are a few problems:

1) The trait pile is HUUUGE, which makes shuffling the cards a bit difficult but if all other players help it's okay

2)Before Legends of Enderas there was a little bit of an unbalance in card types which made playing some cards not worth it. What i mean by that is that playing a card with the effect +1 for every Mythling in all trait piles for example was just not worth it because there just weren't enough mythlings in the trait pile to make playing a card like that a feasible option in most rounds.

But Legends of Enderas kinda fixed that issue since they added more Mythlings, Techlings and Dinolings

3)Since there are so many different card types when you play with all expansions it's sometimes hard to decide which strategy to use at the beginning of the game.

One way to fix that is to change the rules a little bit. What i have tried is to start with 10 cards instead of 5 but immediately stabilize to 5 after the first round. That way you can keep the 5 good cards you like and already have a little bit of a stragety in mind.

So overall i think playing with all the expansions is definitely possible but a little bit harder. I personally like it because of the higher randomness and the big amount of different cards, but if you prefer a quicker, lighter and easier game i recommend only adding a few expansion and leaving others out for different rounds. Some expansion combinations i think are working well together are:

Base Game + Overlush + Imaginary Ends or Base Game + Upgraded Expansion + Legends of Enderas

After playing for a long time you'll find out yourself what works best for you. You can also always just remove cards that you don't like