Dunno if I should have a preference. I mostly visit Malaysia and only occasionally one of the neighboring countries. Perhaps I should consider a cross-border type, as I may also visit Thailand next year.

Let's say I go for a cross-border version....I see so many choices. How to make a final decision? I simply don't know where to start, accept for the fact that I don't want 'Unlimited' as that usually means being throttled all the way. Rather buy as I go as I am not backpacking through Asia, just yearly holiday trips.....within the EU I can simply use my Dutch sim card, so no need for an eSIM in that sense.

This time around I will visit Malaysia (incl. Sabah) and a few days in Singapore....next year most likely Thailand and Malaysia....

Serious question, why so much data needed while travelling?

Cross-border SIMs are almost always not competitively-priced compared to local SIMs.

In your case, Malaysia + Singapore for this trip, can get your Digi SIM on arrival and change to eSIM on the spot (if it is a Digi Store or Digi Express Store at the airport).

With Digi SIM (physical or eSIM), you can sign up many high GB packages for local Malaysia use and using the same SIM then sign up a roaming pass for Singapore use.

Information here and here.

All can be controlled within the app. And Digi so far is the only one that can use international credit cards to pay in its app.