Why not individually wrap pieces?

I noticed this illustration in Thomas Keller’s (Artisan Press) Under Pressure: Cooking Sous Vide. He may address it further, but I have not read that far yet.

Putting things side by side is OK as the thickness is the same for both. Stacking increases the thickness and also the cooking time. This could be an issue if you are trying to maintain a certain texture. If you were cooking something for long time say 2-3 days it would not have any impact

I had previously observed diffficulties bagging chunky vegetables, brussels sprouts and carrot pieces, due to bag material lack of flexibility and elasticity preventing close conformation expelling insulating air.

Are you using a vacuum sealer or the water displacement method? When I vacuum seal items like you mention I use a little more bag and and flatten everything out on the table then pull a vacuum then seal. Works pretty well until veg starts giving off gas and bag expands.

John makes an excellent suggestion regarding using more bag than necessary with vegetables.

SV vegetable cookery could be better suited to using Zip-Loc bags that can be vented during the cook, then using displacement vided again, and resealed.