I did do a search around here and online for how Alliance bonuses stack, but all the answers I find are about the Alliance global items from before the rework. In fact, the only reddit thread I found in searching said that alliance bonuses don't stack at all, which doesn't seem to be the case. Also please note that I play on mobile, so I can't easily test these things, so I appreciate the time of anyone willing to educate me.

Two other disclaimers: I have never played DOTA 2, so I don't have the background of mechanics from that game. Also, I'm unfortunately no good with math, so many of my questions stem from not understanding things there. Apologies to anyone who is annoyed by this. But hopefully this thread can get some good info built up and be referenced later when people have questions.

Flat numbers
I'm assuming that bonuses that give you plus-X (i.e. flat numbers) just stack additively. So Brawny at 2 heroes gives you 30 hp/kill, while the 4 hero bonus gives you 30 hp/kill plus 60 hp/kill, totaling 90 hp/kill. Same with Warrior; 3 hero bonus gives you 10 armor, 6 hero bonus gives you 10 armor plus 15 armor, for 25 armor.

So, first question would be to confirm whether this is correct - if it's not, it changes how I'm thinking of this.

Second question is, are there any exceptions? Or is this pretty universal?

Percentages to do something
Do higher tiers replace lower tiers, or add a percentage of that lower tier? For example, if I'm playing Elusives, on tier 1 I get a 20% chance to evade, and on tier 2 I get 45%. I can't imagine that you are just adding these numbers together, especially since adding the 75% tier 3 bonus would put you over 100. But how does the math work on this? Does percent just not stack, and instead replace the previous tier? Or when I go to tier 2, am I increasing my 20% bonus by 40% (which I think would make it 28%?)?

Also, does this work differently with Assassins, Humans or Hunters?

Percentage buffs
This is really the same question as above, but for Inventors, Mages, Scaled and Warlock. If I have six mages, is it 140% extra magic damage? Or a 100% increase from the 40% that tier 1 grants? Or something else?

Plus attack speed
This is a bit different from the other ones but I thought I'd ask anyway. What do attack speed bonuses do exactly? The troll alliance and certain items give a flat number increase; does this mean that each character has a hidden attack speed stat that this buff increases it by? Just slightly confused since Ogre Magi's spell gives a percent buff so I wasn't sure how all the math worked.

Thanks so much for any help any of you fine folks can provide!