I think g4 Luffy is stronger than a yonko first mate. He just needs extended times period, which I think has happened and will continue to happen. Now, along with extending g4, he just needs to work on mastering all forms of haki and gain experience imo. (He can still awaken)
I think the story will progress to where Luffy will be strong enough to beat a yonko 1 on 1 but not until that's vs Blackbeard. I think he's gonna recieve help all the way until then lol. There too much of an emphasis on him gaining the trust and help of others for them not to continue helping and helping. If luck is a superpower, Luffy has it
I mean really? Physically stronger sure (well depending on commander we are talking about take jozu with two arms i do not believe gear 4th is stronger then diamond could be wrong), But everytime luffy has used gear 4th (in my opinion) only showcases how incomplete it is and how he needs help. Duffy gear 4th wasn't enough to put him down by himself so he needed law plus citizens
Cracker gear 4th wasn't enough to effectively break enough crackers and stamina was it was not a good move to use it luckily he had nami there softening them up and he got to eat them whivh replenished his stamina (cracker is prob the stupidest character in one piece history for not attacking nami once with his cracker soldiers -.-)
Katakuri while luffy did fight him on his own katakuri inflicted harm to himself and it was still pretty close. There is a significant chance that gear 4th isn't enough to put down a healthy katakuri but we will never see them fight again so whos to tell (this is the same with doffy for me i would've liked to see him fight without all his organs being sliced in a instant)
The point is luffys battle have become either a power of friendship (help luffy till enough damage/guard is down then luffy goes in and defeats them, while his friends all believe in him from.sidelines) or a battle of circumstance.
I think gear 4 physically and speed is enough to contend with a yonko level commander person but to outright put them down we have still yet to see that. The only person we know that can do that from the worst generation is obv bb and that angel dude (i always forget his name). I know a lot of people were mad when kaido one shotted luffy but to me he needed that. He's constantly ignoring advice from others and putting people in danger with his decisions. It does make him lovable because it showcases his will but wano is a different ball game i am truly excited to see how it will end