Sure nobody makes actual new original amigas. But they are not rare, while they didn't do as well in the US as they should have. The did still do pretty well, especially in games. For example EA used Amigas. Deluxe Paint is the internal EA graphics tool that they then made public. It introduced the IFF file format, which with Commodore they Standardized. To this day games still use the IFF format. Maya will export to IFF, The Sims games still use IFF. Internal data formats stored on Discs of "the big 3"( legal reasons) still use a variant of IFF to store and hold data for level loading. the AIFF audio file format which you mainly only see on MacOS these days, is also part of the original IFF standard. Just Apple had to Apple and make it their own unique format so they changed the endian order and thus AIFF.
That being said you can do it in software with
https://aros.sourceforge.io/
https://www.aeros-os.org/
https://www.morphos-team.net/
https://www.amigaos.net/
on new hardware, or raspberry Pi's etc AEROS gives you linux as well as modern Amiga + 68K Amiga emulation.
For hardware there is ARMiga(
https://www.armigaproject.com/) there are also
http://wiki.apollo-accelerators.com/dok ... a-v4:start which are the standalone versions, for non AGA there is also things such as
https://www.arananet.net/pedidos/produc ... pre-order/
https://www.arananet.net/pedidos/produc ... -preorder/
which come up from time to time.
MISTer cores also.
Or WinUAE emulator on PC.
For USB some amigas have PMCIA slots so you just use a PMCIA usb card, or you can add some PCI slots to your amiga and then use a USB PCI card, or there are some custom adapters, or the accelerators above add usb.
But such things are academic when the main benefit is CRT monitor and direct hardware mouse
There is also Deluxe Paint II for MS-DOS but it really needs a DOS machine. Its not as good as V or IV or well even III but it what the used to make DOOM.
If you don't trust me on DP being superior here is Mike Ferrari whom did the graphics for the Lucas Arts G.T.As as well as Thumbleweed park.
https://www.youtube.com/watch?v=aMcJ1Jvtef0 for reference the new magic tool that he speaks of in this video is not out yet, we have talked to Mike about it(last couple of months), its "still in the works" though.
Tablet vs Mouse : its not the screen resolution but the resolution of what you are drawing.
If you are making a title screen in 320x200 sure tablet would be great because you are going to be drawing lines and shapes 100+ pixels and you are going for the overall shape and design.
If you are in 1024x768 but making a 32x48 sprite tablet is now useless as now you are plotting pixels.
i.e you are not going to draw Mario with a tablet, you need to plot each pixel to hint at the shape rather than "draw" it. Your not going to draw shades and then slowly built up the colours and layers. You have 16, you will pick them, and then place each colour for the shading by hand. However I would agree the older "Puck" tablets would be just as good if not better for such a use case, as they have more buttons.
How do you adjust the PAR in your head on the fly?
SNES vs Amiga 8:7 vs 26:25. Making a 48x48 massive sprite, ok sure now you need to make an adjustment. So the Amiga is almost 1:1 but turn on "Be Square" and then Deluxe paint will do the 1:1 calculations for you, so the SNES is off by 1/8, i.e for every 8 pixels you go across the height is 1 less (although you probably want to split the difference), so if you are doing 48x48 you draw out the 48x48 circle then disable "circle mode" and squish it back in 6 pixels. 32x32 you squish about 4, 16x16 you can do 1 or 2 but your probably in a pattern and need to fill it anyway. Not doing a perfect mul8 size then make the judgement call, load it up in the preview tool and see.