If a check is made out to two individuals with "and" between names but has JTWRS behind their names, do both individuals need to endorse to cash this check?

All JTWRS means is Joint Owners With Rights of Survivorship, so if one of the people died, the other could bring in a death certificate, sign just him, and claim the funds.

I would interpret "and" as requiring both signatures or deposit to a joint account of those persons (where they have appointed one another as agent under the account agreement).