Found the connections on Reddit:
Both of them begin their lives as incredibly smart but unassuming young men, with loving but seemingly overbearing parent(s.) They both at this time were also separated from their friends in some way (Deku's bullying at the hands of former-friend Bakugo making him chronically-friendless, and Miles being taken away from his old school and all of his old friends by his parents sending him to a better school.)
• However, after a series of events both through sheer chance and accident would end up in the possession of a great power, one that comes attached with a great responsibility (Deku receiving One for All and Miles getting bit by the radioactive spider.) This will be expanded upon in a later connection as to why this is specific to Miles and Deku in a more direct and philosophical way.
• Them gaining these new powers also relates to the fall of their homes protector, a hero who was known as a symbol of hope and goodness by everyone, at the hands of a villain in a black suit in a battle Miles and Deku where there to witness in person (All Might losing One for All in his battle with All for One, and Peter Parker dying at the hands of Kingpin.)
• This would lead to Deku and Miles trying to push themselves harder and harder to become heroes to fill in where their predecessors fell, however along the way there would be many hiccups, as well as doubters. Particularly two people who believed that Deku and Miles did not deserve the powers they got and believed it should have gone to someone else, and acted antagonistically towards them for it (Sir Nighteye and Spiderman 2099) (edited)
• Unlike their predecessors, both Deku and Miles are commonly shown to have powers relating to electricity (Deku's One For All lightning that constantly courses over his body, and Miles' Venom Blasts and signature Shoulder Touch.) They also have more abilities overall than their predecessors, like Deku's various quirks and Miles' invisibility.
• Their main nemesis is a dark reflection of their own journey as heroes, ones who are intent on proving themselves as the ultimate evil to their worlds (Shigaraki and the Spot, who much like their heroes where previously nobodies who's powers are gained from accident and chance much like Miles and Deku, with Shigaraki wanting to become the Symbol of Evil and Spot wanting to prove himself as Miles' arch nemesis.)
• They both have an arc in their movies where they want to save everyone no matter the cost to themselves, which leads to a large group of people having to basically swarm them in order to try and stop them (Deku going on his Vigilante arc to try and take down villains on his own despite it clearly f*cking him up, leading to Class 1-A having to have an intervention with him. For Miles this comes in the form of him trying to stop his canon event and save his father, getting the whole Spider Society on his ass for it except Hobie cuz Hobie is the GOAT)
• They both also, throughout their journey, meet another person who could have used the power that Deku and Miles received but didn't, leading to them being darker and more antagonistic or seemingly-antagonistic (Shinso, who was seen as villain-material for his power yet Deku states that if he had OFA things would have gone differently, and Prowler Miles who should have gotten the Spider Bite but didn't which ended up leading him to become the Prowler.) • Both of them have a mentor who is an outwardly-lazy and disheveled hero (Aizawa and Peter B Parker,) as well as a female ally in pink who they may or may not get together with (Ochaco and Spider Woman/Spider Gwen,) and various other allies that line up pretty well.
• Okay...time for philosophy. The initial power of both One for All and the powers of Spiderman boil down to "with great power comes great responsibility." One hero for all mankind, as Wiz put it in Death Battle, the one hero who's duty it is to save everyone. This is demonstrated well by their mentors, All Might and Peter, who took this to heart but it's shown that their solo-quest to be that hero f*cks them up. Deku and Miles' journey with the power however explicitly refutes this. While they shoulder the great responsibility that comes with the power, their greatest accomplishments throughout the story, their arcs and what they prove to their mentors is that the greatest heroes are not lone-gunmen who shoulder the burdens of the world, but are instead a group, ones who share this burden with others and work together as a team. In this, Deku creates something of an "all for all." Think about it, his fight with Overhaul was only won because of Mirio holding off the villain at first, and Eri lending him her power to go 100%. His battle with Wolfram in the first MHA movie was only won alongside All Might, same with Nine in the second movie which was only won with Bakugo. His battle with Shigaraki in the manga was only able to occur because of the other heroes holding him off, etc. As for Miles, the final battle of the first movie was all about Miles and the other Spidermen (and two Spiderwomen) working together. Beforehand they all believed that only one person could send them all home but Miles proves that if they work together and do it together, they can truly win. And at the end of Across, it is shown he cannot save his dad and fix his canon event alone, and as such a group of other Spidermen rally behind his cause and come to help him. I may not have explained this well but it makes sense in my head
• For a tiny filler connection, both of their original suits are ill-fitting dollar-tree knock-off suits because that's really all they had access to (Deku's suit his mom made him and Miles' spiderman merch,) but they eventually get a more specially designed one. Both of their outfits (and Miles' powers obviously) are based on an animal (a rabbit and a spider.)
