For Vehicles:
Sicarian tanks are totally worth it (regular, Venerator, and Arcus, avoid the plasma and gatling cannon variants).
Leviathan Dreads are beast mode, but cost as much as a Land Raider.
If you run a lot of Terminators, a Deredeo with a pavise (adds +1 to Invulnerable saves) can push your Justarians over the top.
A Fire Raptor is an excellent gunship, but a bit on the expensive side. You can also look at the Imperial Lightning (if Forge World ever brings it back) or the Xiphon for a cheaper alternative.
The Storm Eagle is like a mini-Thunderhawk and is a great transport, but the SoH have access to...
Anvillus pattern Dreadclaw Drop Pods. Totally worth it. Might not look like much on paper, but watch your opponent squirm when your drop pod takes off and starts to flame units it flies over...
For Units:
Legion Consul Moritat with bolt pistols and jump pack, along with a Destroyer squad with Jump Packs and a Missile Launcher and suspension harness with Rad Missiles is a fearsome combination.
With the huge nerf to Veterans, the SoH Reaver Squads are now very attractive. I like to take mine with chain axes for maximum benefit of SoH rules.
A Legion Support Squad with 10 Plasma Rifles is pretty sick and will erase a lot of elite units from the table.
Rapier guns are pretty good (NOT THE RAD VERSIONS. Don't be "That Guy"

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Looks like you got pretty much everything covered. It's recommendations for wargear and squad load outs after that. One comment I'd make: Never put your Praetor in Terminator Armor if you can help it. A Praetor already has a 2+/4++ and a ton more wargear options for way cheaper then any of the Terminator variants. The various types of Terminator armors come with too many disadvantages, like no running, no overwatch, no sweeping advance, etc. For the Sons of Horus, I make my squads as big as feasible or possible to maximize the Legion Traits. I start with two 20 model Legion Tactical Squads with attached Apothecaries and walk them up the table. The sergeants have Artificer Armor, melta bombs, and power swords so I can strike before all those guys with power fists. The Apothecaries have nothing besides
BP/
CCW. They are there for 5+
FNP, nothing more.
As you are sticking with Loyalist SoH, you'll be lacking for a Primarch. Might consider other Lords of War options to deal with them. My #2 rule in 30K: How will I deal with a Primarch and his retinue in a Spartan? My #1 rule: Rule of Cool > All.
Lupercal! Lupercal!