Time Machine external drive with catalina and big sur snapshots

2016 15” MBP Mojave

bought a new EHD for my first TM backup ( will arrive Monday) . Been using superduper to create clones. Once I get a few TM backups want to upgrade to Big Sur ( so after most recent iOS update phone won’t sync or connect w iTunes to sync thus need to move to Big Sur )

EHD to be formatted HFS+ for MOJAVE TM

when I upgrade to Big Sur do I need another EHD for Big Sur TM backups?

will my new EHD be compatible with Big Sur TM backups?

should I partition the new drive?

get a separate EHD for Big Sur?

buy a second EHD??

thinking new file system in Big Sur NOT compatible with my HFS+ Mojave TM

how to format EHD ? If not HFS+

thank you for any help and direction

share without partitioning ??

You should be able to do that. I have a TM with Big Sur and Mojave.