The most important thing is clearly to check out the experiences of others. Every general contractor (GU), every architect, every property developer (BT), etc. has companies they like to work with and those they prefer not to work with (or only at the client’s request). Of course, sometimes there's some favoritism involved, but mostly these companies have proven to be reliable, dependable, and good in the past. Many of the cheap ones (of course not all) regularly deliver poor work or come back later with additional costs. Most architects are interested in a satisfied client, but all want an easy and uncomplicated process. And that usually only works with companies that deliver proper and on-time work. But it also works the other way around. There are many architects and developers that the craftsmen do not want to work with. Either because the prices are so poor, or the planning/management is so bad. The problem is that many GUs put so much pressure on their subs that they often have to drop everything when there’s an emergency. Many trades are only small businesses with fewer than 20 employees, so mixed costing only works to a limited extent; therefore, you certainly need some big clients to guarantee a minimum workload, but also the smaller clients. Not to milk them, but just to be properly paid for reasonable work. Rip-offs don’t work here either, because usually everyone obtains several offers nowadays. If you don’t have to calculate at almost break-even, you might even take a few extra minutes and do the work properly (yes, that’s quite common!). Also, it annoys some business owners that they have to earn their money through “additional services.” Many GUs negotiate with the subs on the basis of “you have to do this and that for the price, but you can charge this price for extra X and extra Y.” In the end, they probably get their money that way, but the craftsman is always the bad rip-off artist and the GU gladly cashes in again and is happy.
Ultimately, the price difference is probably not big. The GU earns more on the trades because he takes a cut, but he can also squeeze the subs more. A good architect, on the other hand, perhaps knows good and affordable craftsmen and can maybe offer a smoother process, even if it might take more time for the builder.
There are also significant differences among architects. First, most architects have a certain style or preference. I often went with my father through new development areas, and you could easily tell from some houses that they came from architect X or Y. Ideally, he should still implement your ideas, but every one of these houses also contains a little bit of the architect’s self-expression. So take a look at corresponding houses beforehand. Also, any extra ultimately costs money with the architect as well. No matter how you build, the simple four-corner house with a gabled roof will probably be the cheapest in the end. Second, there are often big discrepancies between planning and construction supervision with architects. There are architects who are excellent planners but absolute disasters when it comes to supervision/management. The opposite also exists. The drawings are okay but standard or you have to make sure you don’t end up with a messed-up house, but they are perfect construction managers and everything runs smoothly.
This shows: You have to look at all possible options carefully and seek out experiences. Check in your area who is working there and who builds with whom. Some things even a layperson can already see (how work is done, by whom, in what tone, with what equipment, etc.). Otherwise, you’ll also meet builders who usually say quite openly how good or bad it went with whom.