Can you daisy link two inverters together positive to positive neg to neg ac out to increase the watts

This will cause big problems. It will not work and will likely cause both inverters to fail. Power inverters must create the 60Hz sign wave from a crystal controlled internal frequency driver. It's like a clock that keeps the timing at 60Hz. 2 independent units will have slightly different clocks both in time and frequency. This would cause the output waveform of one unit to be out of phase with the second. If they are out of phase, they will look like loads to each other and likely fail. It would be possible if the inverters had a way to link their clocks or use only one clock. This could be designed in however I have never seen this feature. You can hook up multiple inverters to the low voltage side (12VDC), just don't hookup their 120VAC output side. Hope this helps.