Mono-Red is an excellent deck. Adding white comes at a cost, and there’s going to be overlap, so it’s our job to figure out if it’s worth it.
Bomat Courier is as good as they come at 1 mana. It’s a card advantage machine that demands a blocker or spot removal quickly. It’s also an artifact to enable other cards, and this deck features Toolcraft Exemplar in the other slot. To me, this feels like a sure mistake. There isn’t a single other artifact in the 60 outside of Bomat, and you would prefer to be sacrificing your artifacts pretty early on for card advantage. The good news is that Exemplar often demands spot removal from an opponent who doesn’t know how weak they are here, but when those removal spells are cheap instants like Magma Spray and Fatal Push, they can often wait and see. With only 9 white mana sources in the deck, it seems like Rigging Runner would just be a better choice.
Your 2-drops are where you see the biggest upgrades. Earthshaker Khenra is still great, but Glory-Bound Initiate is awesome. In an aggressive deck where so many creatures require removal early, the Initiate can get you far ahead. Honored Crop-Captain is an early creature that rewards you for going wide, but is that really better than what Kari Zev can offer you?
Ahn-Crop Crasher is extremely good, but isn’t great in the Red mirror where cards like Shock can now trade up, and it can be a liability against decks with Whirler Virtuoso and Bristling Hydra. Throw in token strategies that are now prevalent and you can see why this list dips below the usual 4 Crashers. Instead, you also have Captain Lannery Storm. The Captain can hit as hard on an empty board, but it can also help ramp you up to your bigger spells or just play multiple spells in a turn. With cards like Earthshaker Khenra to eternalize, you can always use mana well.
Your top end is the same as Mono-Red’s. You have Hazoret the Fervent and Glorybringer as tough-to-stop haste creatures that go over the top of what most people can do despite being relatively cheap to cast.
So this sort of looks like a deck that may or may not have a higher power level than Red, and may or may not be slightly faster, but it also doesn’t get to play the sweet Deserts that provide some additional late game power. So why go white?
This deck features a main deck Solemnity with the other 3 in the sideboard. This may be asking too much as it’s a dead card against Red and U/B Control, which are two of the biggest decks in the metagame. That said, Energy is still public enemy #1, and this can completely shut them down, making their Whirlers, Hydras, and Harnessed Lightning into bad cards. Factor in that Walking Ballista is so strong against these decks, and maybe you have something here. You even have Lannery Storm making Treasure to help cast white cards!
That playset of Aerial Responders in the sideboard look really effective against opposing aggro decks until you realize they cost double-white and you have literally 9 white lands in your 75 (and you likely want the 15th sideboard card). It’s possible that this isn’t the best way to actually go about Boros Aggro, but it lays out some good ideas. A 5-0 in an MTGO Competitive League is a solid start!