Any idea how minimum satoshis should a UTXO contain in order to be spendable so that fees don’t exceed the UTXO balance ? maybe fees in the future will be so high ?
You can't know the minimum spending balance per input ("input" types easier than "UTXO") without knowing the future fee, which you also can't know.I always use coin control (in Electrum or Bitcoin Core). For each transaction I make, I manually pick the inputs that best fit the purpose based on transaction fee and privacy (linking inputs together). If fees are low, I consolidate more and smaller inputs, if fees are high, I use as little inputs as possible.
Maybe it's a good start to play around with fees on Testnet: get some coins, start Electrum with "--testnet" option, and create some transactions. Send some to yourself, learn how to use "send to many", send some back to the faucet, and see what happens to the fee and your Coins tab. On the Coins tab, manually select the inputs you want to use (the process is a bit different on the latest version of Electrum).
