I'm truly a beginner here. Thanks!
It depends on your budget, of course, but for ISP connections faster than 1 Gbps I would go for the RB5009:
https://mikrotik.com/product/rb5009ug_s_in
which is (roughly) good up to 2.5-3 Gbps (without any trouble).
Cheaper devices tend to max out at around 1 Gbps (in theory) and need some special configurations (that may or may not be possible in your use case) to go faster than that and get to use the full 1.5 Gbps .
Of course you should be aware that the RB5009 only has a 10Gbps SFP+, ONE 2.5Gps RJ45, and the other ports are all 1Gbps.
So "up to 2.5-3 Gbps (without any trouble)" is only achievable when you go through the trouble of connecting your ISP connection to the SFP+, and having multiple systems on the inside of which one can go up to 2.5Gbps....
With 1.5Gbps that would be possible, but only when you are OK with using SFP+ or with having 1Gbps max per single system.
Or you use an CRS305 or even a CRS309 connected via a 10G DAC cable to the RB5005. Then you make that DAC a trunk and break out to your NAS, to your ISP and your other switches via different SFPs or DACs. Not the cheapest solution, but you can have your own 10G backbone.