...How does Savage Worlds work for long campaigns, and deep character story arcs and character leveling?
I've been playing and running SW for 3 editions and I'd say how well it works for long campaigns depends very much on the GM. During a PC's lifetime ther're 5 ranks (Novice, Seasoned, Veteran, Heroic, Legendary) with 4 advancements (equivalent to D&D level ups) per rank. So advancements 0-3 for Novice rank, advancements 4-7 for Seasoned, 8-11 for Veteran, etc. You can use different paces for the frequency of advancements - eg. PC's can advance after every session for short/mini campaigns , or can advance every other session, or ideally every 3rd session for long campaigns, .
If you goal is to run a campaign with weekly sessions that's more than a year long, you need to pace PC progression by having advances every 3rd session, or possibly even less frequently. Otherwise your player's PCs will be at Legendary rank within 4 months (advances every session), or 8 months (advances every 2nd session). I've been surprised with SWADE at how many GMs don't get that and I've played in 2 campaigns where the GM had advancement every session and then bailed around Heroic rank due to PCs becoming to omnipotent. What an advancement grants a PC at Legendary rank slows, but IME PCs becomes too competent at that rank and I typically plan my campaigns to conclude there. In 2 of my homebrewed settings I embrace the concept of generational PCs with inheritance. For those, PCs retire out at legendary rank and a new, younger PC with some form of a bond to them (familial, clan, guild, faction, etc) follows in their footsteps. I sometimes have those 2nd PCs start at Seasoned rank and they may inherit some of their benefactor's gear.
There's no equivalent in SW of XP rewards for every monster/threat elimated, so the focus on advancement is more towards important encounters, whether those be social, explorative or combative in nature. In the previous edition of the rules (Savage World Deluxe) there was a system of XP rewards (1-3 points) for encounters with advancement occuring every 5 XP points. For lengthy campaigns I still sometimes use that system and typically reward 1 or 2 points, with 3 rarely given and only for encounters where the challenge was very steep.
In terms of stories, there's good features in the rules to support it. Most importantly there's Hindrances; somewhat similar to 5e background flaws or bonds. As GM I often exploit those as short adventure hooks, to briefly put that player's PC into the driver seat. Dramatic Tasks have already been mentioned many times, but there's also Social Conflicts which work well to support social encounters. Then there's Interludes, where a player draws a card and depending upon the suit ad-libs an event that occured in their PC's past - not every player's cup of tea, but fun for those who like player-driven narrative.
It's common for SW setting creators to feature adventure generators in their publications. I don't necessarily use them, but I find them helpful in that they show what the author thinks an adventure for their setting should comprise. Some are better than others and one of them (Thrilling Tales pulp) has even been adapted as an Android app. There's also a history with SW content creators using a plot-point model for campaigns. Those are typically good at providing the GM a lot of flexibility with the adventures/missions they run between plot points. Those adventures/missons could be prewritten ones included with the setting book, something the GM rolled up with an adventure generator, or something they homebrewed.
IMO Wizard of the Coast's different editions of D&D are more designed around selling their own settings and campaign books. Whereas SW is more of a toolkit for 3rd parties and homebrewers. Consequently, genre independent story arcs and campaigns are better supported by it.