You don't need the heater. Goldfish are coldwater fish so 74 is getting a little toasty for them. I just keep my tank at room temperature, so it winds up being around 70....but really anywhere between 60-70 is a good range.
If you don't want to do live plants, that's fine, but like others have pointed out, with your intended stocking levels, your nitrates will be climbing pretty steadily. I would recommend keeping some lucky bamboo or pothos in a small HOB filter box, breeder box, etc. to help with nitrates. You won't need to care for them at all and you'll get SOME nitrate eating going on.
As others have also mentioned, 5 fish is too much for your tank. I have a 75, and I probably won't be going over 5 fish. MAYBE 6, if I really really found one I just couldn't live without after that, but then I'd be doing a LOT of water changes and I'd have to upgrade my tank eventually. Unless you're planning on upgrading tanks eventually, stick with 4. Even that's just slightly pushing it, and you will want to keep up on your water changes, doing them large and often.
I'm not familiar with your filter, so I can't offer advice there.
As far as decor goes, fake plants are fine if you don't want the upkeep of live (it really isn't much at all though). Watch out for your decorations though. Don't get decor with holes (these are meant more for small tropical fish and goldfish can very easily get stuck and injure themselves....trust me, I learned the hard way with my pearlie, and he didn't make it after that injury). Don't get decor that is hollow. It traps air that can get stagnant and harm your fish. Don't get decor that is rough or sharp in any way (check your fake plants for this too). Goldfish are SUPER clumsy. You will notice many of us have fairly bare tanks, with not much besides plants. That's for a reason....goldfish are a little derpy. If they can hurt themselves on something, eventually one of them probably will. Round, smooth decor, or things like ceramic pots, etc. are ok for decor.
I wouldn't recommend gravel at all for a goldie tank. 1) It is really easy to trap waste, debris, and other nasties in gravel without you even knowing about it. It's a very messy substrate. 2) They like to forage through substrate, and gravel presents a choking hazard. Unless you want to stick tweezers down your fish's throat (not fun), I'd recommend sand for a goldie tank. My fish love digging through it. If you don't like sand, other options are barebottom (which many people here like for easy maintenance) or LARGE river rocks or glass marbles. Just enough to make a thin layer on the bottom. They will nudge those around and have plenty to dig through, without trapping all that nasty stuff in there. MY personal favorite is definitely sand though.
As far as waterchanges go, here we recommend upwards of 50% weekly. It will depend on your system on what you need. Some people here do 80% 2x a week. I personally do about 75% weekly. You'll just need to keep an eye on your parameters and see how long it takes before you need to change your water. An excellent water conditioner to use is Seachem Prime, or Amquel+. Both are fine, but Prime is more concentrated and lasts longer and is usually cheaper and more readily available. That being said, Amquel+ is still a great product. The reason we recommend these, is because they neutralize ammonia, nitrite, and nitrates as well as dechlorinate your water. They're VERY good products. We also recommend you do any water testing with the API Master Freshwater Test Kit. Amazon is a great place to find those...usually around half off! Strips aren't very reliable, but drops are and this is a brand many of us use and have great success with.
I think that covers everything I wanted to say. If you have any questions don't hesitate to ask, we are here to help! Welcome to Koko's, and good luck!