Use json-rpc without full blockchain So i want trying to use both bitcoin and bitcoin-abc json-rpc on raspberry pi but they will overload the whole pi when downloading and sync @ same time.

So is there anyway to use json-rpc without downloading and sync the whole blockchain or overload the raspberry pi?
if you want to use bitcoin core, you have to install blockchain. maybe you can use prune mode after its totally synced. 

If you want to use JSON-RPC without installing the blockchain, I suggest you use electrum servers. You can send JSON-RPC commands without installing anything. You just connect to someone's server. 

the commands not the same as bitcoin-core, for instance, you can't createrawtransaction but you can get any address balance or transaction details.

if you want to work with bitcoin-cash, You can connect to electrum bitcoin-cash servers.

check electrum protocol methods here.