Quick RDR2 question...

[northwest monkey]

Can you leave all the side missions / Strangers & Freaks missions until the main story mode is completed or are there some that you can't go back to?

I always prefer getting the story out of the way then I can wander about - Fallout 4, Skyrim, RDR all let you play this way & I much prefer it!

[ApexCult]

Some will change if you happen to delay them.

Also in RDR there was at least one quest that changed if you waited until the end to complete it

[Seanseansean]

You loose certain ones after different chapters.
I would do them.