Cycling between FW and Glencoe is not really on, as the A82 is a very busy, fast major trunk road.However there are plenty of options around the town, using the Caledonian Canal and other paths for bikes.Local bike agencies will be able to give you plenty of advice.
The views over to Ben Nevis and the neighbouring mountains from the Gairlochy area are gorgeous.
You could also cycle up Glen Nevis.
I prefer Glencoe to Glen Nevis - you can reach this area via bus or taxi.There are various walk options - check walkhighlands excellent website for details.My own take on enjoying the area (though more suited to having a car) is in the link below:
https://annestravelsandhikes.com/2021/02/13/the-best-of-glencoe/
The train journey to Fort William is stunning for most of the way once you are out of the city.
The town itself is not particularly pretty or picturesque as such workaday at best but it has plenty of amenities and is always busy.`Good local museum too.It’s certainly a good base if you don’t have your own transport.
You can also do the train journey from FW out to Mallaig via Glenfinnan which is just beautiful.And/or out to Arisaig on a sunny day where you can also do a brilliant day trip out to one of the Small Isles - I’d recommend Eigg.
More on the island from my own experience of a number of visits here:
https://annestravelsandhikes.com/2018/07/13/the-beautiful-island-of-eigg-beaches/