Initial thoughts are that if you can comply with whatever SAC you operate under, then there are no obvious restrictions. You don’t want to go below published altitudes or infringe terrain clearance between checkpoints, so by necessity will be at or above - it is a NPA, after all. If ATC have delayed your descent (maybe for good reason) then being a bit high might be unavoidable. If you were capturing an ILS glideslope from above, being high at the OM wouldn’t necessarily be a problem either, as long as you could comply with SOPs.
As far as references go, I can’t find much, apart from in our OM A using RNAV/RNP, where there is a subtle difference between below path deviation, max 75’ at all times, and above path deviation, which is 75’ but only below 1,000’ AAL, so no restriction further back.
Depending on temperature and whether you are correcting for it or not, you are going to be following different paths through the sky, anyway.