In order to stretch relaxers, is it okay that I have weave with braids in it or a sew in 2-3 weeks after a relaxer?
I personally would not recommend getting a weave/sew-in within two weeks after a relaxer. Three weeks would be a much safer amount of time to wait, in my opinion. Four weeks or more would be even better. I say this because the scalp needs to "recover" (for lack of a better word) after a fresh relaxer. Weaves/sew-ins can apply tension to the scalp, and installing one within two weeks can lead to hair loss.
After three to four weeks, weaves/sew-ins that are installed and maintained properly can be a good way to stretch relaxers. Other safer options are braid-outs, cornrow-outs, twist-outs (with perm-rodded ends), ponytail roller sets, and straw sets. Check out this earlier post on styles that blend the new growth with your relaxed ends.
I hope this answers your question!