Do I only need the 3 seeds of the hardware wallet to restore the wallet, or do I also need the master public keys?
I don't know for all hardware wallets, but I know that for Blockstream Jade you need both recovery phrase and xpub to restore your wallet.
Ledger and Trezor are not great for multisig setup, or they didn't fully support it when I last checked, so I would be very careful whit devices you going to use.
To sign I would then need 2 of 3 of the HWW,
but to restore I need all 3 seeds right?
Or are 2 out of 3 enough to restore the wallet ?
Yes, with two keys you can spend keys, and there is no single point of failure, but you need to have all three to restore (unless you have xpub from the lost key).
Is it also possible to create a 2 of 3 multisig with the Bitcoin Core wallet?
I would generally not recommend doing this, unless you are already running Bitcoin node 24/7.
If not than you will have to wait for days for blockchain to download and wallet to sync, not ideal situation when you want to make multisig transaction,
I already have a full node that doesn't run 24/7, but the synchronization is actually fast, it usually takes a maximum of 1 hour until everything is synchronized.
I use the multisig wallet to hold my bitcoins, I make very few payments with it, about 5-6 payments a year
I'm just unsure whether I should use Bitcoin Core for my multisig or Electrum via EPS....
and the HWW I wanted to use would be:
cold card
BitBox
Foundation Device or OneKey.
In your opinion, would this HWW be problem-free for a multisig?