1) Is it possible to have Bubbler Pro track by actual route instead of straight lines from one point to another? 2) Does it automatically use cell coverage for transmitting (both Communication Boxes unchecked)? 3) Would having another GPS app running at the same time cause problems with one or both of the Apps?
To my knowledge, Bubbler doesn't support tracks. So it's limited to the 5-minute interval locations. In SpotWalla you can turn off the line connectors, but depending on your route, it leaves the viewer little information about sequencing.
Unchecking the option to "Only communicate over WifI/Wireless" will allow Bubbler to use whatever connectivity provides it access to spotwalla.com. So cellular or WiFi.
Other GPS devices can cause interference when acquiring its position, but it's more of a phone issue than a Bubbler issue. It's my experience that it's not a huge issue if the devices are at least a foot apart.