There is something called the Power Delivery protocol for use with USB C. If your charger and device both support USB C PD, then everything is fine. The wattage of the charger will limit how fast it can charge, but the PD protocol sorts out the correct voltage. Most laptops, tablets and phones support PD now. You can also buy adapters to go from USB C PD to whatever connector your old laptops use (although watch out for current limits so you don’t fry the adapter). I use this charger for everything. nekteck.com/…/nekteck-65w-usb-c-charger-gan-ii-pd…
On my PD laptop, it complains that it’s a “slow charger” because it wants 100 W or something absurd, but 65 is fine. On my old Lenovo, I have an adapter and the adapter itself doesn’t support high current, so I can’t reasonably use the laptop while charging, but I can charge it while it’s off or asleep. I usually use the OEM chargers for those, but for travel it’s nice to bring less. For everything else it’s perfect.