Yes, they can be cabled when you create the LAG. The normal STP and storm control settings are fine. If they are connected with single links now there shouldn’t be any problem when changing to a LAG. If you do have issues where some are not reporting correctly or working correctly we should troubleshoot those links separately and leave the working ones alone. Typically when the ports report the wrong speed it is a cable issue. Auto negotiation should work fine, but you can try manual if you have issues.  If you create a loop STP will disable one of the links, so unless you want that redudant path it is better to not put loops in. 
Hello.  I have four Powerconnect 2824 switches that I would like to link together using LAG.  I am new to Dell switches and I could use some guidance.  I attempted this with poor results, so any advice would be appreciated.  We are not using any vlans, and everything is on the default of 1.  There are two servers that utilize nic teaming, but they are switch independent teams that do not require LAG on the switches.  My goal is to increase the throughput between the switches.  Should I use the basic LAG layer 2 settings?  Do I need to change any of the default settings on the switch?  Do I have to set up lag on both ends?  I appreciate any advice with this.
Connecting four 2824 switches with LAG guidance