"but it is only 64 Gb"
the thinkpad 8 should use an mSATA ssd so you could upgrade to 128GB (+) and fit it all on the main drive.
You can clone the existing 64 to the 128 then copy/install the band in a box files and realtracks/drums to it - this way you won't have a usb hard drive hanging from it using power.
You can put the old 64 mSATA in a usb 3.0 enclosure or keep it as an OS backup.
Pipeline do you have this type of system? Installed this way running BIAB and RB off of a 128gb drive will leave 28 or so GB for system files and all other programs and data needing to be installed on this Tablet.
I have used BIAB on my new computer for about 2 weeks (13 songs) I already have 15GB of BIAB,RB,.wav and.mp3 data files. That's why I wanted a 2TB drive, My external drive is a 4TB my cloud. $179.00