You won't have issues for wireless connection but for may have problems with the bumper as it is made specifically for the ROG Phone 5, so the size and cut-outs are not the same since the ROG Phone 5 have slightly different dimensions (the ROG Phone 5 is just slightly bigger). If possible, try looking for the ROG 3 version, the main difference is logo on it; the ROG 3 version has a purple-ish logo design whereas the ROG Phone 5 version has red wordings and the logo 'ROG Phone 5 Compatible'.
Perhaps the mods can help confirm if it can still work even if the bumper is slightly bigger?