How much will I save on fees really though that's my question. I get paid out from slushpool every .02 and my list of coins in electrum is really long so I figure big transactions of moving lots of coins I could pay less fees.
The answer is... it depends.
The two main factors will be how many UTXOs do you have? (that is to say, in Electrum, how many individual entries are on the "coins" tab?)... and what the fee "rates" are like when you create a transaction.
In terms of %, the numbers often quoted for fee reduction are:
Legacy (aka P2PKH) transaction: 226 bytes
Nested SegWit (aka P2SH-P2WPKH) tx: 168 bytes =~ 26% saving
Native SegWit (aka P2WPKH aka bc1) tx: 141 bytes =~ 38% saving
However, those values are for your "typical" 1 input, 2 output type transactions. Using something like the coinb.in/#fees calculator you can mess around with different values and we can see:
100 "legacy" inputs + 2 outputs = Chargable Transaction Size: 14874 bytes
100 "Nested SegWit" inputs + 2 outputs = Chargable Transaction Size: 10076 bytes
A difference of ~32%... which would equate to quite a substantial amount of BTC in times like this when BTC is pumping and "recommended" fees start pushing the 100+ sats/vByte mark!
Although, you'd probably be advised to wait until the network isn't quite as busy and aim for that sweet sweet 1 sat/vByte fee rate
One other thing to consider... is it possible to increase the slushpool minimum payout level so that you generate less UTXOs in the first place?
