Scizor, Venusaur, and Delta form Questions

So I’m trying to figure out a good EV spread for Mega Scizor and find out more about the pros and cons of the different spreads on him. I’ve checked out Smogon and various other forums online, but I can’t seem to find any more thorough explanations.

Primary EV Spread I have found is a more bulkier set that utilizes a massive spread and Sword’s Dance. ADAMANT HP 248 (Apparently there are some insane calculations that prove 248>252 when stealth rocks are in play for Scizor) Atk 16 (Guess to hit a little harder and surpass a certain checkpoint with the Adamant Nature) Def 60 (Confused by this. He has a solid 100 base defense and an outstanding 140 in mega. Is this to survive until his mega transformation since he is rather slow? Even so, is it worth this investment???) SpD 124 (Investment in Special Defense makes him an insanely bulky threat especially with one of the best typing combination available in the game… but why 124? This continues into… Speed 60 (adds base 15 speed to Scizor)

Speed 60 is my biggest question. 60 Speed gives Scizor 80 base and mega Scizor 90 base speed respectively. Most forums have told me that this is necessary to out-speed mega Venusaur… but it doesn’t, at least in its base form. Venusaur (both base and mega form) possess a base speed of 80, and most run 20 EV speed bringing that base up to 84 in order to counter some of its common threats.

This means that Venusaur in both forms (84) outspeeds base form Scizor (80). If the investment is simply for Mega Scizor to outpace Venusaur in either form, then why not invest 40 instead?

The other two Scizor sets I commonly see are the ubiquitous 252atk 252spd and a 248hp 252spdef set, neither of which utilize Roost. What are there particular benefits? The first I can only seeing it hitting harder at the cost of massive bulk… so it seems kind of useless unless you know for sure you’re going to be able to set up freely or die after one/two attacks… and the other seems like a super simplified version of the most popular spread?

Okay now leading on to my second set of questions… Why is delta scizor OU in Insurgence? Ice/Fighting is an atrocious typing leaving it more vulnerable than a newborn baby, imo lol…

Delta Scyther seems superior since it can at least outspeed many opponents… and with the future (is this confirmed?) introduction of eviolite, I can only see it being the far superior choice (since typing stays the same).

Yeah a bunch of people agree that Delta Scyther is better than D Scizor. (Yes, eviolite will be in game)

Don’t use eviolite on a frail offensive mon with a shit defensive typing. Life Orb > Eviolite. Regardless, Delta Scyther is still superior.

yeah and there’s always the band or scarf