UTXOs can be used as inputs for your transactions. Your transaction fee will be decided by transaction size and fee rate. Transaction size depends on your input number (more inputs, bigger size) and your address types.

https://jlopp.github.io/bitcoin-transaction-size-calculator/
https://bitcoinops.org/en/tools/calc-size/
https://bitcoindata.science/plot-your-transaction-in-mempool.html

You have to check mempools to use good fee rate.
https://mempool.space/
https://jochen-hoenicke.de/queue/#BTC%20(default%20mempool),24h,weight

This Telegram bot Bitcoin Fees - fees and tx tracker gives you good notifications.

Fees are not forever cheap or forever high. Mempools can change with time so does transaction fee.

When fee rates are cheap, consolidate your small UTXOs