There seems to be much info on this around but three questions I cannot figure out
1. Do miners pick up a double spend if it is not using FSS RBF eg..
Some miners support FSS RBF, some support Full RBF, some support Opt-in RBF, and some don't support any form of RBF at all. Furthermore, your transaction has to propagate, so a lot of full nodes need to support whatever RBF you use, and that is also local node policy.
RBF is part of local node policy so it all depends on the miner and there is no unified "miners support ..." for node policy.
I use Electrum and have a unconfirmed transaction of over 24 hours is still unconfirmed. I can make a new wallet by reseeding in electrum and the unconfirmed will not show up as it builds actual transactions. - can I just now send the money with a higher fee to myself elsewhere and will the miners pick it up and negate the other ?
Opt-in RBF is the most supported form of RBF. Electrum has the option to enable Opt-in RBF in your transactions and to increase the fee of said transactions.
AFAIK, Electrum does not have the ability to create any other RBF transaction (i.e. you can't force it by clearing all unconfirmed transactions).
2. If the above is untrue and I use FSS RBF, all the examples online show how to use coinb.in to replace a transaction that has one input and output. How do i do it when the original transaction combined 4 or 5 addresses to get the total to send?
"Combining address" just means having more than one input. Just make a transaction with more than one input.
3. If as another person pointed out if my input has to be fully spent and there is nothing left to add to the fee how exactly do I add more to the replacment transaciton (Do i just add another input ? if so could someone tell me how on coinb.in?)
Yes. You need to add another input.
I would not use coinb.in for this for two reasons. First of all, AFAIK, coinb.in uses Bitcoin Core as their backend node (i.e. transactions are validated and sent via it) and Bitcoin Core does not support FSS or Full RBF. It only supports Opt-in RBF so you won't be able to make and send any RBF transactions without opting-in in the original transaction. Secondly, I have experienced issues with their signing code; it does not appear to actually sign transactions properly.