First, I would like to stress that I have no hands-on experience with any GSM ROM. I have a CDMA device. So, with that in mind:

The first thing you need to do is get familiar with fastboot. You used fastboot to unlock your bootloader, and you'll need to continue to use it to flash ROMs, unless you get 4EXT (found here: [TOUCHCOVERY] ORIGINAL | 4EXT Recovery Touch v1.0.0.5 RC1 with SmartFlash for s-on - xda-developers) with it's new S-ON Unlocked mode. If you want to do things manually, I have a guide that will show you some easy steps (although it's meant for those that still need to unlock): http://androidforums.com/evo-3d-all...ms-kernels-using-fastboot-updated-3-26-a.html The second post will give you GSM device instructions.

The second is choosing a ROM. You can find a list of ROMs here: EVO 3D GSM Android Development - xda-developers

I would recommend these two ROMs:

[ROM]LeeDrOiD 3D V5.4[KERNEL] V5.4 2nd April |Aroma|Tweaks|Fast|Stable|Beats - xda-developers

[ROM] - [3/21/2012] - MikRunny v1.13 - [Sense 3.5 | 2.3.5 | Tweaks | Odex | GSM] - xda-developers

Both have what you're looking for in a ROM. But there may be another ROM or two in there that suits your needs. They both have OC'd kernels built in. My guide (that I linked) will show you how to flash them.

And remember, Quadrant numbers are just that, numbers. I had a slick setup that was ultra fast and Quadrant told me that my device registered 1500. But if you're set on using a benchmark app, I'd recommend AnTuTu. Anything over 5000 is wicked quick.

 

You can flash an OC kernel onto the stock ROM and be able to OC it. I just don't know of a good kernel for GSM devices. But the XDA thread list should have something.

 

I was unable to load the video before, or else I would have told you to avoid that kernel. IIRC, RCMix is a CDMA only kernel.

I did find this kernel:

[KERNEL 4-14-12][ROM 4-4-12][Anryl] shooter_u (DE-)SENSE 3.0 stable OC - xda-developers

And check out this thread for ROMs:

[INDEX] HTC Evo 3D GSM Development *FULL LIST* - 17.04.2012 - - xda-developers

 

Now that you're unlocked with HTC method, you don't need to unlock again, unless you choose to relock. Or you can go one step further and do the S-OFF HBOOT downgrade, but I would suggest you hold off on that until you get comfortable with doing all this stuff.

You can make a backup of your system in recovery. Most recoveries call it "Backup", but users will call it "NANDroid" or a "NAND backup". It's the same thing. Make a backup, this is very important!

Then you could download and flash that GSM ROM with ICS and Sense 4.0. Wipe everything (factory reset, clear cache/dalvik). If you don't like the ROM, or it doesn't work, you can restore your previous backup and it's like nothing happened.

You really should look over my guide on how to flash and root. It'll walk you through everything you need to do.

 

I'm not 100% confident in this, but I think you can just do fastboot oem unlock and you should be fine with no data wipes. I wasn't able to find a temp root so you could make a backup, so a wipe might be unavoidable. Sorry

And no, S-OFF (it means security off, instead of S-ON which is security on - this allows you to flash radios and other things) is not required. You just need to access recovery through fastboot (fastboot boot recovery.img) to flash kernels properly. Or use 4EXT recovery (recommended!). However, S-OFF is preferable to S-ON unlocked. Once you get more comfortable with rooting, you'll see why. Then feel free to ask about getting S-OFF and I might be able to help you with that.