You can load Seedsigner with 3 keys at once, then sign the transaction.
Power it down, it wipes itself.
Basically all you need to store safely are the seeds.
The user experience is fantastic & makes multisig convenient.
3of5 is ideal btw.
Discussion
If you wanted to add in multi vendor security,
Id just buy a Foundation or Jade along with it or build a Specter DiY.
Anything that can handle QR PSBT & SeedQR.
Foundation should be adding SeedQR in it's next release 🤞.
SeedSigner only multisig > SingleSig w PP
Two vendor Multisig > over complicated setups
Just my 1nak.