Details on WestJet benefits (and benefits for all Delta partners) for Medallion status members are here:

https://www.delta.com/us/en/skymiles...yteam-benefits

While that webpage doesn't specify it, Silver Medallion members get zone 2 boarding when flying WS ... which is the same as WestJet Silver members.

(Note that there are a bunch of WestJet exclusions listed on that Delta Medallion member page, i.e. no Guaranteed Reservation, Priority Immigration, Priority Reservation Waitlist and Priority Standby - none of which are WestJet things - and "Preferred Seats are currently not available for Silver Medallion Members flying on WestJet.")