Don't know what this has to do with ABGX360 but to answer the questions of the post itself
DVD modding right now... it has been years since the last banwave. You can still screw it up hard enough that something could happen but even a basic concept of what you are doing and some sanity checks will keep you clear.
Any kind of game modding, save modding and then going online or having it on your system. Expect a ban. Said class of mods really needs a JTAG or RGH machine as well -- all the old disc swap methods are tedious or gone really, and don't keep you safe either.
Actually going online. Ban city.
There are some exceptionally annoying (and not free) methods in stealth servers and all that jazz.
Mainly as every COD player with an eye towards modding things that I have met wants to mod the online multiplayer I will assume that is the case here too. Surprising me it seems COD WAW has a meaningful LAN option so you might have that as a possibility (if the game has a LAN play option you can set up a VPN and play with others on it, depending upon the mod done maybe even other stock players as I think it is only the host system which needs the modded setup). For games with LAN modes might as well start with
http://www.co-optimus.com/games.php?system=1&lan=true&playerCount=2&countDirection=at least
I imagine GTA is more for the single player.
If it is just COD and GTA4 that you care about I am probably supposed to say consider grabbing a PC for this -- both games are reasonably old at this point and thus will work on fairly modest machines by the standards of the current day (
http://www.game-debate.com/games/index.php?g_id=28&game=Call of Duty 5: World at War and
http://www.game-debate.com/games/index.php?g_id=77&game=Grand Theft Auto IV&pc are both machines you can probably buy the box and a suitable graphics card for with the same sort of money you are likely to lay out for the necessary mods if you don't solder it all yourself). Furthermore where this 360 stuff is a pain to mod, indeed few do it, the PC fully embraces it and has done years --
https://www.moddb.com/mods?filter=t&kw=&released=&genre=&theme=&players=&timeframe=&game=11544 and
https://www.gtainside.com/en/gta4/mods/
If COD WAW single player is what you want to mod or you are content with the VPN stuff then there are other options for keeping online. Dual NAND RGH will allow you to have a hacked NAND and all that follows from it and boot back into a stock machine to do online stuff with. Not many do them these days, or indeed ever, but it is an option that I should mention as part of this. Obviously you have to be careful about what appears on your profile for if you get things it should not have from the hacked side of things then it might get troubled. Speaking of profiles
Profile wise they tend to only get upset when you mod the profile, achievements and do things of that nature and I don't think I have ever seen it spread across a system to other accounts unless they similarly get things they should not have. I can't say that would always be the case but it would be a first. For the most part that system gets banned and that is the end of that, copy profile to a new one if you want to.
If you really want to head down this path and a PC is not an option I would instead suggest a sacrificial 360 (Jasper if original or any kind of newer take, guide here
https://gbatemp.net/threads/guide-how-to-hack-your-360.334203/ so you can see what you will need, should not be too hard to find one going fairly cheap), sacrificial accounts and that sort of thing. Can't help you with the stealth setups, partially as we don't really do it around here and also because I actively ignore most things happening in that world.