Does Firefox allow websites to use my location when calculating results?

You can hide location. Settings > Permissions and data. Which doesn't do much, but that it what the Free VPN is for, to hide your IP address etc. when you are using Fx

However if you don't have GPS on your device the best any site can do is to see where your IP server is.

In the UK where I am the location is at least 200 miles from where I reside.

When out and about the location is the server I connect to via Wi-fi

This article has the details: Does Firefox share my location with websites?

Generally, the sites might "guesstimate" at first, and separately potentially ask for geolocation permission — that can be granted temporarily or permanently (and managed later; also shown in the address bar when being actively leveraged by the site) — the precise location comes usually from the device (so Firefox asks for the relevant permissions from your system then) using either its hardware (precise) or software (e.g. wifi ID triangulation) capabilities. If neither is available, Mozilla has a fallback service to help with geolocation if the system can't provide the option, yet the user would like to tell a site more relevant location, so even if device grant is not permitted, but site location is allowed, there's still a fallback mechanism.

My tip: if you don't want to manage site permissions and check how they're storing the data, use those sites in Private Window when granting the permission — that way it's a) always only temporary for the session, and b) if the site then saves your location for later, it will also get wiped when you close it;)