Just wanted the recommendations in using azure frontdoor or azure traffic manager for my 2 different web apps hosted on different regions? Can we use both together?
IMHO you should use the one that makes more sense. Traffic Manager you can work with different algorithms when routing to the right region, while Front Door you don't have this flexibility.
On the other hand, Front Door offers some features like Web Application Firewall (WAF) and SSL Offloading that may be interesting in your scenario.