I’m sure someone has calculated the hours needed to buy with in-game grind estimates.
I’m okay/not okay depending how ridiculous the grind is. It can also be remedied so I’d like to be optimistic.
You can't buy or early unlock the items included inside the free or paid Warbonds (battle passes) to be unlocked, they are only unlocked by playing with medals (rewards by completing missions, you get extra ones when playing in harder difficulty or completing secondary objectives).
You can't buy or early unlock the new Strategems (summonable special attacks or items with cooldown), they are only unlocked by playing using a currancy you get as score for completing missions or secondary misson objectives Major Orders (Major Orders = secondary objectives completed across multiple missions, stuff like 'complete X missions of Y type'). The other mission reward you get is XP, which is used to unlock them).
You can't buy or early unlock the new Ship Modules (passive upgrades like reducing cooldown for some Stratagem types, reducing reload times, improving deployment times...), they are only unlocked by playing. You get them using as currency probes with samples you find in Points of Interest (POIs) exploring during missions, you unlock them with XP.
You can only pay with real money to get/early unlock the paid Warbond (smaller than the free one) and to get customizables in a rotating store that has limited items. These are paid with Super Credits, that can be earned as free and Warbond unlocks or found as collectables in Points of Interests (POIs) loot.
The paid Warbond costs 1000 Super Credits, you can get 800SC from the free Warbond and 300SC from the paid one, plus earning around 10-40 per hour by playing. Assuming you play 10 hours per week, you'd get 400-1600SC per month depending on your playstyle.
Oooo. I’m not a fan of the paywalled guns.
There aren't paywalled guns. All weapon types are unlocked in the free warbond or the Stratagems by playing.
You can pay to get the premium Warbond (which you can get for free by playing, see above) but you'll have to unlock its items by playing. To get the premium Warbond or guns from the store you use Super Credits, that can be bought with real money but also unlocking them in the free and paid Warbonds plus as exploring for loot in points of interest. Nothing in the game is behind a paywall, everything can be unlocked.
In addition to this, weapons from the rotating store and premium Warbonds are basically skins of the ones you unock in the free wardbond: same weapon types, only with different appearance and minor stats changes.
Are premium warbonds accessible with in-game currency or only thru real world money?
Yes, see what I posted above.