As you intend to use for business, as you suggested, I would avoid the learner machines. As it's for business, as has been mentioned above, Prusa products are amazing. If 6" is for sure your largest build, Mini+ would suffice with a build surface of 7"x7"x7". If you may go large, look at the MK3S+, or if you want really large, and multiple extruders, there's the new Prusa XL.

For your tiny models, or possibly even your 6" model, resin printers give better detail than FDM. However, in my limited experience with resin, I have found that resin prints are much more brittle, where FDM prints can take a little more abuse before breaking.

Either way, do some more reading, get to know the different materials and what advantages/downfalls/dangers each present. For example, for resin you need to wear the proper PPE as it is toxic in it's uncured form, or for FDM, some plastics like ABS, may need filtration, as fumes can also be toxic. I very occasionally print resin, but usually print PETG or PLA, so I don't bother with enclosures and filtration, but do wear gloves to handle resin.