First, welcome to this site! You'll find a number of folks here who have a lot of knowledge about Macs, and also are helpful.
Secondly, as I mentioned in my post above, I plan on getting the 2018 model with a 256 gig SSD and 8 gig of Ram, but with the Core i5 processor. I believe that Core i5 processor will be at least as fast (and maybe faster) than the Core i7 processor inside my current late 2012 Mac Mini. And that model costs about $1100.
The Core i7 2018 model, with a 512 gig SSD and 8 gig of Ram, costs about $1600:
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And the one with a 256 gig SSD costs $200 less:
Shop Apple Mac mini Desktop Intel Core i7 8GB Memory 256GB Solid State Drive products at Best Buy. Find low everyday prices and buy online for delivery or in-store pick-up. Price Match Guarantee.
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But again, and especially with your processing tasks very similar to mine, the Core i5 processor should do you well.
Also, you can go with the 256 gig SSD, and if needed, add an external SSD later on. With my current machine, I am only using about 75 gig of space, and I have 3 external SSDs. Two of them I use for backups (along with storing some miscellaneous files (mostly movies and TV series)), and the third one I also store some stuff, but I also use it for testing a new version of the Mac OS (I did that with Catalina, and last year with Mojave).
One reason why the amount of space I am using on the internal SSD is not much is that I make a concerted effort to do as much cleanup as I can on my own, and also use two excellent programs (Onyx and Tech Tool Pro) for additional cleanup, plus maintenance (and rarely, if ever, repairs). Having that much free space has at least 2 benefits:
1. The machine runs faster and smoother, especially with some applications.
2. If I need to download a somewhat large file, I have plenty of space to accommodate such a download.