how to know when you need to raise beta blcoker dose?

Helloo, I have a pcp check up in about a month and im trying to prepare. My doctor doesnt know a ton about POTS but is super accomidating and willing to educate herself on medications or ideas I bring in so I like to check and see what works with you guys here. I do pretty ok with my walking hr (like 110-130) but my hr gets much higher with stairs and hills still (160-180 or higher). I currently day 25 mg XR metoprolol and im wondering if I should up it so I can handle stairs and inclines better (currently i mostly avoid them unless its a very short flight). The only thing that I worry about is I already have low resting HRs, even before beta blockers (40s-50s when fully relaxed) so i get nervous about uping any. Alternatively could guanfacine help instead? I do have overactive adernaline at times and stress makes my POTS much worse.