Protein powder has always been more of a convenience to me rather that a dietary staple. I do like to eat around 1g of protein per pound of body weight (220g) so if I'm not looking to eat large quantities of chicken, smoked turkey, white fish, or the occasional red meat then I consume around 2 scoops per day. (50g) More often than not, to ensure that I am achieving my protein intake goals, the scoops of protein are added into my morning oatmeal just to start the day without worrying about having multiple servings of meat for dinner or before bed.
I don't necessarily consume protein bars all that much just because they are more likely to be filled with fats & carbs. These are macronutrients that I would much rather prefer to spend on foods I really enjoy. However, protein bars are good in a pinch when traveling or short on time due to their high availability.
One thing that I would suggest when purchasing protein based supplements is to 1) do your homework and 2) don't skimp on a quality brand simply because it is slightly pricer.
Doing your homework: There is an endless supply of reviews for products on the internet these days. There is no excuse for buying a protein that contains a flavor that you don't enjoy, or one that is an overall poor quality product. Before you buy, invest the time to find out which mixes easiest, which is the tastiest, and which digests the best.
Don't skimp: Buying protein is just like buying any other food in the grocery store. You get what you pay for. It may seem like a good idea to go down to the local general merchandise store and pick up a budget-friendly protein powder, but you can't expect that product to compete with a higher tier product. Even just reading the nutritional information on the product often gives away what kind of quality it contains. Some brands are notorious for using fillers in their products in order to limit their costs. These fillers are more than likely going to show up as carbohydrates in the product, more specifically as sugar. Look for a products that is low in calories, high in protein, and low in fat and carbs. This will more than likely be a protein isolate product.
If you're on a limited budget, using lower quality products is understandable. If you see that your product may potentially have a sizable amount of filler, I would suggest to consume minimal amounts of it on a daily basis. Also, it is best to consume this product before bed due the fact that you may have a harder time to digest the protein. This will prevent you from having to deal will going through your day with a bloated and uncomfortable feeling.
Conclusion: Protein powders and bars are an efficient and convenient way to ensure you are hitting your goals for protein for the day. However, there is no need to heavily rely on them to the point that you are not eating quality whole foods. Use moderation!