With the compressor pretty much, but you'll need to adjust based on taste and even play with different compressors as they're attack and release curves will change the way the sound behaves. Just gotta experiment a bit. I can tell you that for this particular application I really really like vladg's Molot. I know it is written in the Cyrillic alphabet, but there is an English option and I like to do this in the "Alpha" mode because it isn't quite as aggressive. It is preference and I've used different compressors for the application just based on various things from changes to the timbre to fitting better in with the other instruments.
Compression in general is quite a complex topic and it'd take me way too long to explain in any reasonable detail about how it works or the various ways to use to manipulate space or even forcing one without a sidechain input to react in an almost dynamic EQ kinda way. But with that being said you've really just gotta experiment with it to find something that really works for you. I can tell you that I have a lot of compressors because I find unlike EQs I can get more color out of them and that is typically what I end up doing on a lot of sounds. Rather than using them strictly for mixing.
I say compression on the guitars because even though distorted guitars are already quite compressed it isn't the end all be all to further coloring them with compression Much to learn about that you do! But some things you can try to give the guitars some more weight. Put on a different hat for distortion for a minute. Think of distortion as a way to generate new and extra harmonics that you can then manipulate to your advantage. For example you could try some frequency selective parallel distortion to add in some extra girth that you can then mix in with the original to give them more heft if they're missing it. Kind of like the old trick of gating a tone generator from a kick to make it beefier in the mix. Since you have 4 guitars in this particular case then I would look at doing something a bit different personally. I'd take two of them and hard pan them and leave them mostly alone (EQ, compression, etc.) but pan the other's about midway left and right then play with distortion on them and make those heavier sounding. This would likely widen the mix with two different guitar layers at two different stereo positions, but would also have the effect of making the center seem "heavier" and leaving the sides "lighter" further adding to width without really sacrificing any mono compatibility
As for the synths, I mean they kinda work. The brass is actually a pretty good sounding brass stab, but it sounds like it came from a ROMpler of some description. I like the piano quite a bit, and I love the sync lead but it is so buried and overshadowed by everything else in that section that it kind of loses its impact While this may sound kind of biased or such, I really really dislike guitars lol. Not because there is anything wrong with them, but just because I'm not a guitar guy and everyone talking about them makes it sound like there are humongous differences between ancient humbucklers and modern ones. Look Solid body vs Hollow Body? Easily understandable differences in sound. But I feel arguing about a 139048 year old humbuckler is like the synth guys saying that there is a huge difference in the way a 50 year old Minimoog sounds versus a clone from like Studio Electronics. Look is there a difference? Probably, but is it worth all that money for it? Probably not. I'm a synth head and I love synths. It is easier to impress me with guitars than it is with synths. Suuns' 2020 (warning epileptic seizure warning) has a guitar sound that I love because I've never really heard it before and plus it is super creepy and unsettling. The bass is a synth and super dark and brooding. Both of those sounds impress me. Mord Fustang's Lick the Rainbow (terrible name I know), but this has quite a few synth sounds that just impress me. Still trying to figure out that bass sound myself. So much breath and life in that. Your synth sounds aren't bad, but if you want something to really show you what is possible with just one synth, then look no further than KVR's One Synth Challenge (I've entered a few myself) and let me tell you some of the sounds people are able to coax out of these synths is simply astounding.