Unfortunately there's some incorrect information in the guide. It would have been a good idea to hop into the Samus discord to ask some questions before doing this.
Dr. Jay said:
First off Dark Samus has a faster back roll, while samus has a faster forward roll. Its barely noticeable but Dark Samus has an easier time rolling back to punish an attack like melee samus with wave dash back.
Incorrect. Dark Samus has a faster roll both forwards and backwards by 3 frames. 3 frames is essentially nothing though and it likely won't make much difference in general gameplay. But Dark Samus' rolls are both faster, albeit marginally.
Samus:
Backroll FAF40 (Invulnerability 5-20)
Forward roll FAF35 (Invulnerability 4-18)
Spotdodge FAF27 (Invulnerability 3-17)
Dark Samus:
Backroll FAF37 (Invulnerability 5-20)
Forward roll FAF32 (Invulnerability 4-18)
Spotdodge FAF27 (Invulnerability 3-17)
(Thanks to KayJay for that research).
Dr. Jay said:
Dark samus’ projectiles all go lower to the ground. The big takeaway here is that Dark Samus is better against shorter characters, characters with extremely low ducks like shiek, characters with shorter short hops, and characters that use explosives.
While Dark Samus' missiles ARE slightly lower than Samus', it actually makes no difference in gameplay. Missiles from both characters will miss and hit the same crouching opponents.
The only case where this makes a difference is charge shot. Dark Samus' charge shot, even baby CS, will hit lower than Samus' charge shot. This means it's better at hitting opponents hanging on the ledge or 2-framing them. Pichu for example can crouch under Samus' uncharged CS but not Dark Samus' uncharged CS. This is the only projectile where it makes a difference.
Dr. Jay said:
Well aside from those differences everything about samus and Dark Samus plays the same,
You actually neglected to mention the arguably biggest difference between the two (well, you kind of mentioned it in passing when talking about the shield but didn't elaborate on it). That being that Dark Samus has larger hurtboxes due to her animations. This is most prominently seen on her roll, double jump, idle animation, and dash dance.
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On the actual play guide, Samus is not a zoner nor a defensive character, and never has been. It's a common misconception because she has multiple projectiles, but she's really not. She operates in a kind of middle ground area, needing to alternate between distancing herself and going in with an optimal spacing. She'll straight up lose in a zoning competition with actual true zoners (Mega Man, Pacman, Villager, Duck Hunt Duo, Toon Link etc) and she'll also lose in a straight boxing match against true rushdown characters (Fox, Falco, most swordies, Sonic, etc). Optimally she needs to sit in a middle ground of playing neither overly defensive nor overly aggressive.
She's got plenty of offensive options that don't revolve around the use of her projectiles, evading or shield breaks. You barely mentioned her tilts, especially ftilt that can be angled up or down, and up tilt that is still a really strong tool that can no longer be ground teched in Ultimate, meaning a guaranteed popup. No mention of up air combos either which can combo into itself or into other aerials, all of which are strong options. Nair and Bair still remain fantastic horizontal kill moves, Dair remains a super powerful spike. Nothing about bomb combos and follow ups. Nothing about how great she is at edge guarding, including bomb usage to cover ledge getup options.
She also has plenty of defensive options that don't involve projectiles either. You only mentioned up b out of shield in passing on one occasion, nothing about charge cancelling into grabs or other moves, and I don't think you even mentioned zair as a combat tool even once, why? It's an essential part of her spacing game even though it's been altered since Smash 4.
I'll leave it there as I just wanted to cover some of the major points. If you want to, please pop into the Samuscord to discuss the character in more detail, we have a team that's been labbing the character extensively since release.