For me, the best way to level ever:
Count the number of encounters until gaining the next level!
It is about 8 or 10 encounters per level.
But the first tier (levels 1 to 4) advances faster, such as 4, 5, 6, and 7 encounters until level 5. Oppositely, if you are in a sweet spot, or want to slow down advancement, you can double the number of encounters to 16 or 20 before gaining the next level.
Finally, a Moderate challenge is worth 1 encounter. But an encounter that turns out to be easy is only worth ½ an encounter. A hard encounter is worth 1½ encounters. And a near TPK is worth 2 encounters. DM and players can decide the difficulty AFTER the encounter is over. Sometimes an encounter that the DM expected to be difficult, turns out to be an easy cakewalk. And oppositely, an encounter that was supposed to be easy or moderate might end in an near TPK. So decide the difficulty afterward.
No XP. No milestones.
Just count encounters. So simple, and much more accurate.