I mean, just in general he was a genious, but also like many geniouses, he fell prey to a shit ton of nonsense. From how I understand it, he spent equal time and believed in equal importance on his study of physics, alchemy and finding hidden codes in numerology of the bible.
Sense of humor and personality, no clue, don't think that generally is super strongly carried in surviving literature.
My math prof told me he just paved over the small, itsy bitsy problem that all of his equations fell apart if any value was zero... so he just ignored it. Then Leibniz seen it and fixed everything to solve for that pesky little issue of dividing by zero.
Leibniz discovered calculus on his own without intervention from newton, also probably before newton, also his notation is basically what we use today.
newton looked at calculus from a physical pov, velocity -- acceleration.
Leibniz came from more of a 'number theory' perspective, (although i dont believe that term would have existed) this is why his formulations covered a wider field of numbers.