Best toggles:

1. Inactive button coincides with the background / Active button has a highlighting background. "we suggest you use a combination of saturated lively color (ideally corresponding with your CTA color scheme) and a light grayscale neutral color. "
2. Active button has a check sign
3. Active button has bold text (a bigger font size helps too)

About the 5-second and 20-second tests:

The results confirmed our expectations since the average error rate was lower in the 20-second tests and the Success-Confidence score was higher. However, these differences were not significant.

There is a difference of 0.5% in the error rate and 2.5% in the confidence score.

The ticks could be perceived as outdated (akin to a physical form more than a website). As for radio button icons, you might as well use a radio button instead.