Years after the surgery, the risk of "stretching" should be none.
I don't know how long you've had the surgery. If you just recently had it, take it easy for a month or two. Don't lift heavy things, that's all. Not until 2 months or so, if you workout with weights.
But from my experience of 3 HT via FUT, within a couple of months, like 3 months, the redness is lessen. 4 months to 6, gone. (This might depend on a person.) And after 3 months, heavy weight lifting should be fine. After 6, forget about it.
About visible scar, if it should happen, repair of hair transplant donor scar can be done many HT doctors--possibly yours. Some doctors will do it for free because they messed up.
Don't know anything about #guard razor or swimming.
Wishing you the best.