Beginner questions - primary fermenter, sugars

The starter kit I bought came with a 10 gallon pail with a lid, not airtight, and no space for an airlock. I know many winemakers do not use an airlock during the primary stage. I wasn't able to find an answer on this but did find most people using an airlock in the primary stage for beer. Will not using an airlock during primary affect the final product or will it end up more or less the same?

Secondly, I'm been thinking of buying something like the muntons kit enhancer instead of using just dextrose, does it make a difference? One difference is $2 instead of $8. I guess one way would be just to try it but I was just wondering what your thoughts were.

regards.

You can get away without an air lock, some breweries don't even have lids on the feremnters,
It's a precaution and a sensible one at that. If it's a viable option to fit one then I would. If not just put the lid on but don't seal it.
There are 3 problems to over come. Release of CO2, blow of for a large krausen and then keeping a sanitised brew.

As for sugar. I would never add it unless it's a trusted balance recipe and it's required.
If it's purely added because it's a cheap way to up the ABV on a poor recipe then the beer will be worse for it. Most of the commercial busters are better than sugar but I'd have to question if they are a better option than pure malt. I don't have any real experience on using them so I can give a definative answer but those are my thoughts on the topic.