It depends on the start-up temps if a 5W-30 grade oil will really be much thinner than a 10W-30 grade oil
0W-30 grade oils usually are alway's thinner across the temp range, except the famous German Castrol 0W-30.
I'm using Shell Helix 0W-30, UOA is on the way after 19700 km.
And yes.. use the OEM Honda filter: 15400-PCX-004
And double YES: keep your eye on the level: check it frequently.
Even if you think you've figured out what the engine uses it still may decide to use a little more so just make a habbit checking the level.
IMO stay away, far away from "racing oils" in the xW-50/60 grades.
Not good for the oil circulation at 9000 rpm (or 8000 if you have an AP2)
Even the xxW-40 grade oils are not really necessary, Honda (IMO!) mentioned it because of the 5W, not the 40.
0/5/10W-30 grade oils are the way to go.
Have fun driving top down