You don't need a separate path, but you may want to make a separate game folder, and save your program and scoring files in that directory. However, if you decide you do want a separate directory folder, inside your local game folder, you can either use the full path, like C:\qb64|mygame\scores\ or just the relative path, scores\ in the file access statement. You can also use QB64 keywords like _CWD$ to find the path you are running in, if you want to use a full path call.
Anyway, I use RA files, so I can overwrite scores. You may want to take a look at my ASCII Invaders game, in the Competition Discussion thread. Sequential files are fine, but you generally have to load the whole file into an array, change the arrays based upon game results, and then open the file for OUTPUT and write the arrays back into the file. I suppose if you don't want to use fields or make a fixed length file, as used in RA files, sequential is your best bet.
Pete