What to spend money on for decor

It looks like the second photo has minimal decor and I think that looks just fine! We are doing centerpieces, which are provided by our venue, decorating our sweetheart table, we got a floral arrangement from our florist for the fireplace we will be sitting in front of, and we are doing a memory table. We might decorate our cake table a bit depending on what we decide we want our cake to look like. Otherwise, you really don't need a ton. Another cute inexpensive idea that I've seen done is some couples will take photos of themselves from their homes and decorate various areas with them so you can walk around and look at their photos throughout their years, I've also seen photo collages that are put around the room.

It's personal preference. I don't believe that your venue style dictates what decoration you use. Some people prefer simple decor styles while others prefer elaborate and neither is right or wrong. Most guests generally don't remember your decorations unless they tend to obstruct conversations across the table.

Guests don't notice or care what ceilings/floor/chairs look like because they are focused on the couple and having fun with other guests.