For MAS Enrich only, the best is:
1st: HSBC Premier Travel Mastercard. RM1 (overseas spend only) gives 1.1 Enrich
2nd: CIMB Travel Elite Mastercard. RM1 (local and overseas spend) give 1.0 Enrich

For other airlines, e.g. Krisflyer, Asiamiles, etc. other cards such as Maybank or UOB are better.

Currently, I am focused on accumulating Enrich because MAS has a special category of economy class tickets for Enrich redemption which is quite good - typically available if you search several months in advance of travel dates.

Yes. HSBC Premier Travel Air Miles (1 Air Mile = 1Enrich) awarded are capped at 20,000 Air Miles for overseas spend and 30,000 Air Miles for local spend per calendar month.

The FX conversion rate used has an additional 1% fee built in. That's why some others have commented that it is "expensive". I travel overseas regularly for work and get reimbursed for whatever I actually spend - so the FX conversion rate applied by the credit card is acceptable for me. The CIMB Travel Elite card FX rate on foreign spend is better because it doesn't have this extra 1% fee.

So far this year, I have travelled to Hong Kong economy return costing 25,600 Enrich plus RM348 taxes & fees. Phuket economy return 13,200 Enrich plus RM205 taxes & fees.