I guess all guys here are correct but you better stay 2 levels bellow maximum initially, to see how bumpy it actually is. And only then climb to OPTIMUM. All the protections are there in LNAV, but as the angle of attack is changing in turbulent air you might be very quickly without any margin (especially in turns).
I have heard some rumours about -800’s with winglets to have some problems flying on top in bumpy air. (Optimum and maximum FL are little too close)
(My understanding is that bank angle selection is only available in HDG SEL and VOR modes.)
You are right about HDG SEL bank angle limit but it is not taken into consideration during LOC interception. So joining LOC it might go over.
Happy landings.