MechHeaters

Here's the mechs I can think of you can build with the items in your inventory, since you want your first mech to be a heat we'll go for that 

I notice you had the zarkares at max mythical so I suggest you to use this build but this will be temporary because of the second heat mech build which is this:
Once you upgraded the MPV you can switch it with zarkares and have a little more space to also replace iron plating with savior resistance
 
For the second mech I choose to make a physical mech due to having some of your physical items upgraded 

I made this build in case you want to build this although I don't highly suggest to use this build because of energy mechs you might face in arena that can your drain your energy quickly and you won't get to fight back due to having no weapons that are energy free, so here's the other build you can use that might be able to fight back against those:
With the annihilation this can somehow fight back energy mechs even when your energy had been drained
 
Now for the 3rd mech this is the build I only came up with
You can replace the ultrabright with another malice beam if in case you get one for extra energy drain 
Also the items I used to those builds are mostly E-M in case you don't have some of it you can get them pretty much easily eventually 
 

Here's the mechs I can think of you can build with the items in your inventory, since you want your first mech to be a heat we'll go for that 

I notice you had the zarkares at max mythical so I suggest you to use this build but this will be temporary because of the second heat mech build which is this:
Once you upgraded the MPV you can switch it with zarkares and have a little more space to also replace iron plating with savior resistance
 
For the second mech I choose to make a physical mech due to having some of your physical items upgraded 

I made this build in case you want to build this although I don't highly suggest to use this build because of energy mechs you might face in arena that can your drain your energy quickly and you won't get to fight back due to having no weapons that are energy free, so here's the other build you can use that might be able to fight back against those:
With the annihilation this can somehow fight back energy mechs even when your energy had been drained
 
Now for the 3rd mech this is the build I only came up with
You can replace the ultrabright with another malice beam if in case you get one for extra energy drain 
Also the items I used to those builds are mostly E-M in case you don't have some of it you can get them pretty much easily eventually 
 

The score on your raid determines on how much HP you had lost on that raid which means it does affect it negatively and yes it is the same when having any backfire weapons and drones that you use on the raid which is why using those in the raid will have your score will be reduced more from the backfire

Just go to arena then do some matches and after making 3 wins you'll move up to a higher rank