Just a thought for you and anyone else looking at this option with the 27": Consider going for the high end model instead. There's a weird almost counter-intuitive price scale at play here when converting the fusion drive to an ssd:
27 base ($1799) + 512 ssd = $2099
27 medium ($1999) + 512 ssd = $2299
27 high end ($2299) + 512 ssd = $2399
As you can see above, simply ticking that 512gb ssd option drops the price gap between the base model and the highest one to only $300. What do you get in return:
The base and medium have a 32GB SSD. The high has a 128GB SSD (because coupled to a 2TB HDD and the already probably 'too small' 32GB for 1TB is almost certainly in the "too small" at that point. ). It is a 4x bigger SSD, so get a bigger 'credit' too apply to the 512GBSSD cost. Basically it is about $100 for the 128GB and $100 for the 2TB HDD which shaves the jump down to $100 ( instead of $300). Apple BTO math the 2TB HDD is worth $100 more than the 1TB HDD.
Apple's hyper SSD $/GB pricing somewhat bites them in the butt here (appears that way). The 'credit' for the 128GB is much higher which passes in a discount. I highly doubt they mind much. There is lots of margin padding slop in any of the highest end configurations. You just spend $300 more from basic to high on those right hand sized above.
a.) a much faster cpu (while still an i5, the high end standard cpu is a 9th gen vs the 8th gen in the other models)
b.) a much faster gpu
c.) more vram
It costs more and you get more. Also paid over $300 for a 512GB SSD too though. If your workload involves modifying lots of files though the SSD is probably worth it as it is a better match to APFS.