This thread doesn’t exactly relate to you, but it does cover a lot of the same ground you might look at, so do read it. It may suggest some things you haven’t even thought of yet.
Now, to your specific question.
There are two cases.
Either
- you have bought the new expansion (The War Within or Midnight, which includes TWW) or you’re going to, or
- you haven’t, and you want to stay at level 70 instead of going on to 80.
If you have bought the new expansion, you can either
- go to the new expansion, and come back to complete Dragonflight and Shadowlands later, at level 80, or
- stay and finish Sragonflight, then go on to TWW
Either way, when you go back to Shadowlands, youare going to be overpowered for it. (Which, honestly, if you’re going to be OP for something, Shadowlands is probably the best place for it.)
So everything depends on whether you are going to stay at 70, or go on to 80.
If you are going to stay at 70, then
- Finish Dragonflight and Get better gear, not necessarily in that order
- Go back and finish Shadowlands
- Start some new characters of different race and class (“alts”) and play them
- Find something you enjoy doing at or below level 70
If you are going on to 80, then
- Get to 80
- Get better gear. Do some Delves, World Quests, etc
- Make alts if and when you feel like it.
- Wait for the next expansion, Midnight
Please ask if you have more questions, or if this is not clear