You can play back your recorded tracks and record your vocal to a new armed audio track. You will need to use headphones so the instrument sounds don't get recorded in the vocal track.
To get a stereo mix of your instruments, just mix down to wav or mp3.
You can do all mixing in Mixcraft to get the sound you want. You can even setup automation after your vocal is recorded.
Mixcraft8RS(418)64Bit, Win. 10 64Bit, Intel i5 @ 3.20GHz, ssd 250GB(os),1TB hhd(library audio),1TB hhd (recorded audio),Nvidia GeForce1050i video,16GB RAM,Focusrite 18I20 2nd gen usb,Motu 5 ch.midi interface, D5,U220,Keystation88,B4000+,Leslie,Rhodes73mk1