You should unlock vanity items with the relics first and then unlock the Hero weapons by trying new loadouts and using leftover relics. It's a much better use of your relics since you can unlock Hero weapons by just playing the game, and it'll also extend your interest in playing because you'll be trying new playstyles every week or so. That's what I did and I have everything unlocked now.
You can get more than 5,000 relics. Even though there is a limit, they still transfer, although this is happening on my account that already had over 5,000 before I updated the app. Maybe if you start completely from scratch you are truly limited, but it's not even possible to get 5,000 relics with the new payouts now. I downloaded the app on a second iPhone and I have 2,000 versus 7,375 on the non-updated app.
Also, I saw a few people using the top hat a few weeks ago. Either they were the developers of the app, work for ND/Sony, or the hat was a preorder bonus in some region.
When you go into custom loadouts it tells you what's required to unlock weapons, Mysticala, Sidekicks, Gear, Heavy Weapons, Boosters, and Loadout points. Without knowing your play style my advice would be to stick with a weapon you're comfortable with and always have either the Para .45 or the Pistole equipped. Since you're new and don't know the maps as well, I'd equip the Savior sidekick to help you out in case you get downed away from teammates. I'd also urgently advise you to equip Explosive Awareness 3 as soon as you can. It allows you to disable Mines and C4. I'd also have at least two loadouts that have Mines and Grenades in them--in case the other team has Explosive Awareness 3, you can quickly switch loadouts to use a Grenade instead. Lastly, stick to your teammates until you get comfortable with the maps and your shooting abilities.
Hero weapons are special versions that have two mods on them (you're normally allowed one). They're unlocked by getting a certain number of kills with each weapon.
#2 is sort of funny when it happens, especially when you're next to a teammate who's doing the same thing. You look like a pair of clowns. #1 has killed me at least once every other match and is infuriating lol.