This one's leave are a big thicker and a slightly lighter colour on the tips.
Do different varieties have different thicknesses?
Or is this a sign of something?
Final question below

As you can see the seedlings are growing strongly towards the sun.
Will the straighten up when the stalk starts thickening or do I need to start training them with sticks or similar.
Many thanks!
Have 6/10 germinated and growing. Still hoping a couple more might sprout!

Three answers! I grew a hundred seedlings last year, and the 40 I kept all survived and are looking good.
The first true leaves mean a lot more than the first cotyledons, and yes each variety looks unique. I had vastly different looking ones, some were reddish, some varieties grew long skinny leaves etc.
You don't need to do much with them until they've got a few sets of leaves. Then what I did at the recommendation of the person I got my seeds from (Fuzzy in HI) I transplanted each little plant in its own gallon pot. At first it seems like too big, but at a year old now they are very happy and still have plenty of room.
Simply rotating them will help keep them straight. My yearlings are all different... Some are curved and some are straight but they are pretty short still so no worries about staking. You will see that in a year or so they actually start getting "trunks".

Great. Thanks Disneyhorse.
I will rotate the pots this morning!