Any Manual mode flash should work with the radio triggers. One exception would be the Nikon SB-400, which needs connection to the camera menu to work at all.
Or, that model of flash also includes a builtin optical slave trigger, so that it can trigger in sync from the flash of any other manual mode flash. You would need something like Radio to trigger that first one remotely however. Or you can use radio on both of them.
Manual vs TTL is a big question. Having a little prior flash experience would be helpful to really understand it. Both have to set the flash power level. Manual means it is you that does it.
TTL is automatic point&shoot flash, much like any compact camera does. Subjects vary however, and flash level is not always precisely correct, so often a slight bit of exposure tweaking is necessary, called Flash Compensation. If it is a little too dark or too bright, you simply tweak it a bit for a better result.
Manual flash is pretty easy for one flash. With just a little experience, you will know ahead of time if you want about 1/2 power or about 1/8 power, etc... i.e., you soon learn to just know a fairly close starting point. You see the result on the camera rear LCD, and the histogram can help too. Then you tweak the power level accordingly, to zero in on the exposure, the way you want it. One flash is not hard to do by trial and error, since you quickly learn about what it will need (called experience). Same as last time in same situation.
But for two manual flashes, you have to get the exposure right, but you also have to get the two flashes adjusted relative to each other. Trial and error still works, but two is at least twice as big a job. The easy way is to use a hand held flash meter, to simply set their individual power levels to the value you want them to be.
But regardless if it is TTL or Manual flash, some degree of watching and tweaking is always necessary, to get flash just right.
The Nikon Commander system can individually meter and control two flashes, and you can set the fill light level in the Commander menu, so that the fill light is set perhaps one stop low (ratio). Then you may still have to tweak flash compensation, but you can control the ratio in the Commander menu.
The Nikon Commander makes a hard job easy, and it certainly has some strong advantages, but it also has some strong downsides. One (of several) is that all the commander flashing causes pictures of the subject blinking. This can be controlled and bypassed by the FV Lock feature, but which is not present on camera models without a commander.
I think Manual flash is your answer, it also has some advantages (of control). But of course, it helps to have a way to control it. A hand held flash meter makes it easy. Short of that, I would suggest learning this white towel technique:
Chuck Gardner's White Towel Exposure Method
