Assuming that you intend to continue scanning incoming documents on a regular basis (if you only plan to scan old ones you better get it done at a scan service anyway):
Scan profiles, some scanner producers call it scan presets, will make your work much easier and faster. With a profile/preset you save a combination of scanner driver settings for later reuse. Example: Profile A for plain black print on standard white paper, B for colored magazine articles, C for sales slips of different sizes (e.g. auto-crop to original size instead of scanning small slips at a standardized page sizes), D for thin paper with print on both sides (driver settings e.g. see-through or bleed-through prevention), E for documents with extra length, etc.
Considering the documents you mentioned you will probably get to the point where you need more than 9 scan profiles. Many ADF scanners offer just 9 profiles, some even less. Some producers implement scan profiles in the driver, others in "scan utility" software. Some offer hardware buttons to choose among profiles. Many models with hardware buttons and display just show the profile number without additional text. Will you later remember what profile 3 does? A few scanners have a display that shows text as well, so you can give your profiles speaking names. And more than 9 profiles? Often implemented in software – but such demands get you quickly beyond consumer-grade hardware/software.
I recommend buying a scanner where auto-crop is already supported in the driver. If you have to crop your scans with additional software you have to live with a lot of compromises. So better do not count on upgrading this feature with additional software at a later stage. Reliable auto-crop is very hard to implement on the software level alone (and requires quite some CPU power). Even if a consumer-level third-party software claims to support auto-crop you will get a lot of false results (from not enough cropped to cropped too much, to even cropped completely at random - there is consumer and semi-professional software for around 200 USD that cropped completely at random in my tests).
Why did I not limit my answer to hardware? Because buying a scanner is not like buying a printer as those that did not use a document scanner before might think. The print dialogue is more or less standardized and variations are quite limited across the many printer producers and models we use for our general printing needs. WIA drivers (Windows) for scanners are similarly standardized but you get only a fraction of your scanner's capabilities. TWAIN drivers are a completely different story. If you have no prior experience with scanner drivers and image processing, the time necessary for understanding and using your scanner's driver and scan utility software to its full potential can vary a lot depending on the scanner's producer and even the producer's model. And even after you understood one model you might be lost with another one to the point that you want to through it out of your window.
Once you bought your scanner, you are stuck with its driver(s) and scan utility software – assuming you are not prepared to go beyond your budget with additional third-party software or you are not willing or able to patch your workflow with scripts or manually go through process steps with a number of free or open source software. If you are willing to spend additionally for additional image processing capabilities, more scan profiles, more automation (file naming, distributing files to specific folders, etc.) it gets expensive quickly because you enter a market focused on larger companies that is only slowly moving towards small companies with limited IT resources. Your scanning needs overlap with the needs of many small companies or SOHOs.