I've raised English Lops on and off for a few years, and have looked heavily into the Checkers.
I recommend the ELops WAY over the Checkered Giants. My experience with the ELops' personalities has been absolutely positive- Generally, they are friendly, outgoing bunnies, and many breeders describe their personality as "puppy dog like". They can be silly and clownish (mostly my bucks have been like this), and temperament-wise, they make great pets. That said, I experienced a lot of health problems in the breed, even with ELops from different lines. I tried to breed a lot of those issues out, but in general, they are just not a healthy breed.
Checkered Giants are INTENSE. They are a LARGE running breed, meaning they are meant to run on the show table, not be posed still like other breeds. I own a English Spot and have owned a Rhinelander, both running breeds, and while I would describe both their personalities as energetic, they are nothing compared with the high strung, and even aggressive attitudes seen in the Checkereds. Checks are not commonly kept as pets, and are rarely ever sold as pets, and it shows in their temperaments. They are not cuddly rabbits, they are not sweet, and they are not a breed you want to get into if you want a laid back breed. This is what breeders of CGs have told me, and what I have observed from the judging of the breed at shows (I've seen barricades put up to keep the Checkers from going after people and other bunnies on the judging table).
Check need LARGE, solid-flooring housing; we're talking 5-6ft long hutches with a lot of height space. It's recommended that these bunnies also get daily exercise outside their cages; they are extremely energetic, and need to get that energy out. Keep in mind that being a marked breed, it is much harder to breed a show quality Checker, and you will get a lot of unshowable mismarked. You need to have an appropriate outlet for these culls, as this is NOT a breed that should be sold as pets. Checks are not common, and you won't have a lot of show competition, or many other breeders to sell to or buy stock from.
That all said, YES there can be nice Checkered Giants, and YES there can be mean English Lops (I had one aggressive ELop buck a while back who I euthanized, so it does happen!), but in general, if you want a nice tempered rabbit, go for the ELops. Don't get me wrong; I LOVE the CGs and I definitely want to get into them one day, but I would not recommend them as a first time breed, especially to a youth. I totally understand your goal of wanting to breed a nice tempered line of Checkers (I do too, some day!), but definitely try your hands on a breed that is more manageable before jumping into a breed that is so intense.