Sigh. Perhaps. You're positive that they're not using resources if they appear in that "list" as long as background refreshing is disabled?
What do you think this 'Background App Refresh' setting means? That it is just there for decorative purposes? Background App Refresh means that apps can wake up for limited periods of time (essentially the OS monitors their actual usage and if, eg, an email client were to check for emails only once per hour, the OS then only allows the app to wake up once per hour, apps can abuse this system but the OS naturally tries to differentiate between network calls that actually resulted in data flowing and spurious once that don't result in anything). But off means off for this category.
There are exceptions to this rule [that apps don't do anything with Background App Refresh disabled]:
a) apps can request a couple of minutes to finish certain tasks when the app is put into the background, eg, finishing a down- or upload, I think the maximum is five minutes for this at the moment (the precise number has changed over the years)
b) apps can play audio in the background but it is generally pretty obvious when an app is doing so (in particular since only one app can do so at any given moment)
c) apps can request location information (similar to Background App Refresh) that can be shut off globally or per app basis, if that is used, the 'compass arrow' is visible in the status bar, in the Location Services settings you can also see which app is currently using location services and which app has used it in the last 24 hours
d) apps can provide active navigation or VoIP services while in the background, that is indicated via a coloured status bar
e) there used to be an exception for VoIP listening for calls in the background but it seems that got replaced with push notifications
There is also the built-in fitness tracking of the OS (although these data can be accessed via the Health app, they are collected independently by the OS, the Health app is just one of the apps that can access them, third-party apps can access them to). It is background activity that is not linked to any app running and it can be switched off in Settings > Privacy > Motion & Fitness). There are other background processes of the OS that can be switched off: Location Services for stuff like compass calibration, setting the time zone, help with WiFi networking and many more like Bluetooth, 3G/4G, WiFi, iCloud syncing, backup, etc..
Usage monitoring per app can be done for: the aforementioned Location Services, the amount of data used via cellular, the amount of battery power (General > Usage > Battery Usage). In there, apps with genuine background activity have that label (for me that is currently Mail, Glympse and Skype, though apps using less than 1% of battery power aren't listed, nevertheless, the listed apps' battery usage adds up to 100%, ie, there isn't much battery usage by less-than-one-percent-usage apps). There is a third-party app called System which shows you (similar to Activity Monitor on the Mac) the current CPU, memory and network usage and the list of running processes. The only third-party processes I can recognise in there are Skype and Nimbuzz (with Background App Refresh switched off), and if I remove both apps via the task switcher, they disappear from that list. This means the exception (e) for VoIP still seems to be there in some form and removing these two apps from the app switcher does stop their activity (though Skype is listed as only having consumed only 1% of battery, so this isn't doing much harm).
As I said, I have 100 apps in my app switcher. I can guarantee you they are not all running in the background (the unix-like list of processes in the third-party app System would be showing any processes if there were any running ones).