Am I getting this right - you have an arp running and add some notes manually while this is running - and record to the same track, or?
For timing and midi and what you heard - I come to think of setting for midi if to use asio latency compensation.
This basically means that if running asio buffers at 256 or higher - the delay that produced from realtime is compensated for or not when placing midi on timeline. You can probably notice 128 samples as well as you mention supertight, so I’d go to 64 - or turn off latency compensation for midi track.
Is it this setting in Preferences possibly that needs to be changed - but this is for new tracks?
There is also a track control button to be made visible - which is not visible by default as I recall.
So this can be set for each track if to place note in time as you heard them - or compensated for asio delay.
And track recording arp should maybe not comepensate for asio latency, since it’s generated by midi clock - not in realtime to what you hear.
Maybe I got this wrong what you do - then just ignore…