B&H Photo Has the Top-End 16-inch 2019 MacBook Pro in Stock — this is the one you want as the single travel/desktop machine
For how to use a laptop as a desktop computer, see:
This machine below is the cat’s meow for anyone who wants high performance (not the highest possible, very high) and a single computer for desktop usage and travel—none of the extra expense and hassle of syncing two systems.
I strongly recommend at least a 4TB SSD but the 8TB SSD (more than twice as much usable space) is the smart move if used heavily and for some years to come. You cannot buy any external SSD that is as fast or convenient as the internal one, and an additional $1100 for an other 4TB of ultra-fast SSD storage is a steal—.
As much as the OWC Thunderblade is the best-ever external SSD (that I use every day and is critical to me), a big internal SSD is even faster and more convenient—unless one needs to high performance storage moved between machines, so it is apropos for that purpose.
Below, the 8TB SSD model just went back in-stock as I write this.