Well there's to things you seem to be lumping together. Wireless performance and Internet performance. First, what is your Internet service? Usually the bottleneck is the Internet service and not anything related to wireless or SOHO router performance. Next it could be a wireless issue because I'm assuming you're running a single SOHO wireless router. SOHO wireless routers are not designed to handle that many wireless clients. Enterprise access points can vary in the number of connected devices depending on what the clients are doing. If it's web surfing, you can typically cram more wireless clients on a single AP versus devices which are taxing the network by doing streaming.
You need to provide a budget as this will dictate the design of the system and the equipment to be selected.
You can have everything on wireless and have very good performance. But equipment like this comes at a cost. You mention wanting have everything wired. I assume your home isn't prewired. If this is the case, are you going to have cabling pulled and network drops installed in the walls? Or are you just going to have cabling out in the open across the floor? This will also answer whether a patch panel would be appropriate or not.
You mention PoE for possible use with IP cameras. There are two flavors (actually three) but two which are relevant for you. One is PoE or IEEE 802.3af and PoE+ or IEEE 802.3at. The difference between the two is PoE is spec'd to provide power up to 15.4 Watts. PoE+ is spec'd to provide up to 30W of power. The third I sort of glossed over is to provide power around 60W. Obviously going with a switch which can do PoE+ will inflate your costs. When looking at a switch, you have to determine how many PoE/PoE+ devices you're going to run. Then you select the switch based on the overall power draw. Some switches can provide full power across all PoE ports. Some can't and there's power budgeting at play which balances out power load. My suggestion is to look at PoE+ capable switches. The reason being, it provides the greatest amount of flexibility. Most devices will run on PoE such as APs, IP cameras, VoIP phones, and even small 5 port switches (which I have two in my home network operating this way). But more and more devices are starting to require PoE+. These include newer high performance APs and IP cameras with PTZ (pan/tilt/zoom). I have 2 (soon to be 3) 802.11ac capable APs which require PoE+ power to perform at maximum spec. All my IP cameras run only on PoE along with my VoIP phones.
How critical is the network to you? Are you going to combine your business with the home/personal use? If the network is critical to you in terms of up time, you might want to consider switches with dual power supplies with each one on separate power circuits/UPS'.
As far as security, I wouldn't look at anything but a UTM (unified threat management) type firewall. A regular SOHO and even SMB firewall/router won't cut it. You want something that has content filtering which will allow you to control the type of sites users are visiting on your network. Ideally, you want a next generation firewall which will provide the ability to get deep into the data of the network packet and have rules act on the data contained. SPI firewalls only work on a TCP/UDP port basis. Stuff can be missed by following this now very basic level of security...lots of stuff. These firewalls can do bandwidth quotas and other features based on device or even user login.
For any guest wireless, especially since there's a home business tied to all of this, is to have a captive portal system which requires anyone using it to accept terms and conditions of using the network. Once you have a business in the mix, things change big time and you have to cover yourself legally.
What you want to do can easily be accomplished. It's just how fast are you willing to spend the money.