Any reason not to consider the baseline 2.2 with 256 and utilize a Samsung T5?
If you're sure that you'll never need more than 256GB for system, applications and other internal stuff, why not? Personally, I'd never go for less than 512GB these days, but everyone's needs are different.
The T5 will be slower than the internal drive, yes, but will still be fast enough for almost any use. I use those SSDs to keep and edit my photo libraries (which are growing in size at a much faster rate than internal storage can accommodate) and they're perfect for the job.
512 GB is also my minimum. But for a lot of things the T5 is perfect. I have VMs I use once a week on one and it works great.
Did you have to install any additional software that comes along with the T5 (presumably for garbage collection or firmware updates?) ? I am thinking of getting one for VMs as well to go along with my 15" 2018. Debating between T5 and Sandisk portable SSD (500gb).
Thread Starter: I suggest you determine the your need for the internal ssd size based on the size of programs you plan to install. I keep my internal ssd mostly for installed software (and short term storage) and external for normal storage- no need to keep excess storage baggage of stuff you don't need on a daily basis IMO.