(note -- all these all-time ranks are using times up until Dec 31 2019)
Farah had an all-time kick in championship races and only lost twice, to Jeilan and Edris, over the course of his 2011 - 2017 stretch. While his PRs 12:53 and 26:46 only ranked 34th and 16th respectively (through 12/31/19), he was clearly capable of 12:45 / 26:30 or so with old spikes at his peak form. Plus, Farah owned the indoor 2mile WR before Kerr took it with a 8:03.40 -- I'm sure he could have gone sub 7:30 in the right race as well.
And then in the 1500m -- from the beginning of time to Dec 31 2019, only 14 men had broken 3:29, 42 times -- and Farah had two of those marks, 3:28.81 at Monaco '13 for 11th all time, and a 3:28.93 at Monaco '15. Those are quick times! Obviously, Monaco is a unique place to run fast, but I think that Farah could have been maybe 85% of what Jakob is in circuit 1500s, a few 3:29s and plenty 3:30s / 3:31s (in old spikes). Or a 110% version of 2019-2020 Stewie McSweyn, if you prefer that comparison.
Would Farah have fared well in championship 1500s? I don't think he would have been anywhere near the level of Jakob, but he did show the ability to really turn the wheels in the 5000m. How would he have done in the slow kicking 1500m Rio final or against Kiprop in 2013 or 2015? We'll never know, but I think he would be anywhere between 3rd and 8th in those. His "best" distance, at least PR-wise, would be somewhere between 3000m and 5000m, at his peak.
Essentially, to me Jakob is a much, much, much quicker Farah with a superior aerobic engine, who followed his brothers into the 1500m and chose to contest it -- but like Farah, can clearly dominate the 5000m and should be able to dominate the 10000m for at least six or seven global championships with a skillset like that. Right now, Jakob is clearly at his peak at 3000m but is clearly strong enough to challenge records both below and above at the same time.
Jakob has said for a long time that his best events are well above the 1500m -- he's on the world record chase all the way to Kiptum's mark. Farah moved all the way up late in his career and ran a pair of 2:05s -- I'm confident Jakob will run 2:01 or better one day.
The only other comparison was El G, but I think it's clear that while they approach the 1500m from same direction, Jakob is much stronger and has the capacity (and desire) to push far beyond the 5000m.