landscaping changes after Design Preliminary Review

If your areas in WEc1 have changed, you better update the credit. otherwise the reviewer might just deny you WEc1. It's because changes to PI Forms do trigger a review of any related credits.
This is kind of a predicament, because even if you still meet the credit requirements you are suppose to tell. I have seen other people here not doing it and it's always a judgement call when it comes to changes, if they are big enough that it would change LEED credits or not. However I'm better save than sorry especially if it's just a minor change in the forms.

You are required to confirm for the construction review that the there have been no changes that affect the submitted and approved design documentation.

Before you proceed with the construction review you update the credit status. For approved credits, you can leave the credit as-is, ask for a reevaluation, or remove it.

If you are still in construction and you are not sure whether a credit will change leave all the credits as-is. If something changes later you can ask for a reevaulation by entering the credit and making a request.

Just curious, if you mark a credit to be “re-evaluated”, does the fee increase? Would this be an appeal in a way?

I'm not aware of a limit, but there is likely a limit to the number re-evaluation credits. The GBCI's Certification Policy Manual doesn't state what happens when you select re-evaluation. When you select that option in LEED Online a statement that an additional fee is due does not show up.

This might fall under what is called "reviewer discretion." If the revised credit makes simple changes then likely no big deal. If your site becomes smaller, your building taller, and the energy analysis is completely redone using different systems, then your likely to get a special email message asking for additional fees.

It is not an appeal. You can only do this "re-evaluation" for credits you have already earned. For example, I had a project where we designed all lavatory faucets to have the 0.5 gpm aerators on the faucets. However, the contractor purchased a metering faucet that could not support the 0.5 gpm aerator. While we had already completed both phases of the design review, we were obligated to report the change (LEED requires this). However, we were using metering faucets so it proved non-consequential for our credit as we didn't take account for the metering in the orginal submittal.

You are required to report any changes to the "anticipated" credits from the design review. Your call really if you want to do it in the second phase of the design application or in the construction application.

There is no fee and the only limit is the number of design credits you pursued.

Same question here. If a site plan was submitted in design stage and has been approved, but some changes in the hardscape occur which change the landscape area, I guess we have to submit the relevant WE and SS credits for re-evaluation during construction stage, and update the PIF form as well. The change does not affect transportational credits, but the site plans for these were linked to the PIF form, so the site plans will change. In this case do we have to re-evalute transportational credits as well? will their uploads still be linked to the PIF form and get linked to the new site plan, or will the site plan remain as in Design stage? In the latter case their will be some discrepency between drawings - does this cause any problem?