Felo ratings can only compare relatively fencers within a fencing group. In order to compare between groups (e.g. between two fencing clubs), the initial values must have been estimated realistically and carefully. Unfortunately, descriptions like “above 1600 are the strong leisure fencers” are not very precise. The comparison should work quite well nevertheless.
Of course, it is much better if some fencers fence in both groups. They connect the groups statistically and make the Felo ratings compatible. If appropriate, you may merge the groups in one Felo file, although only few fencers fence in both groups. Theoretically, one common fencer is sufficient, however, he has a lot to do then. For example, if one of both groups was estimated too highly, he shovels the points to the other group until everything is consistent.
Additionally, you can use tournaments for this but it is a lot of work: You must collect all current Felo ratings of all opponents of your fellow fencers.
Be this as it may, the experience with Felo ratings is still to little in order to know how well you can make Felo ratings of different groups comparable by common fencers or tournaments. At least, within a group they work very nicely.
By the way, Felo ratings of different weapons can never be made really comparable because they can never fence against each other. Here, a good initial estimation is the only way to get close to it.