combine solution of SNCP and OLP protection

Yes it is one the cost effective way to provide tertiary fiber protection. even you can also use OLP
 with  your primary OTU for more fiber protection.

When considering SNCP working at electrical layer , you could consider to set following parameters

1.  Hold-off Time (100ms)- this parameter is used to avoid repetitive switchovers when services are unstable,
2.  WTR Time (s)- Services are switched back to their working paths that have restored to normal only after the WTR time preset for the services elapse

As OLP working at optical layer only-no delay you could set , but you need  to set and maintain following parameters

1. Variance Threshold Between Primary and Secondary Input Optical Power (dB)- to generate diffferent maintainance alarm( signal fail (SF),  POWER_DIFF_OVER)

Though OLP is cost effective solution for fiber path protection, however, you need to maintain specific power difference between working and protection path.

Dear friend!
Yes, there are three paths. However, the priority switching may be involved. Therefore, you are advised to set different switching delays for SNCP and OLP. Or one has a switching delay and the other has no switching delay.
Thank you!