Yes. A Studio site is not frozen at launch. Pricing, products, content, and modules can all change while the campaign is live. The one category that needs care is chart sensitive changes, which route through your EVEN team so chart bodies stay notified.
What you can change mid campaign
Pricing can change mid campaign. So can products, including adding a variant or closing one. So can content across the site, and modules, which can be switched on or off as the rollout moves. Every Studio is configured to its rollout in the first place, so changing it as the campaign develops is normal rather than an exception.
Chart sensitive changes
Anything that touches the chart plan goes through your EVEN team. They make the change and keep chart bodies notified, which is the part that protects eligibility. If you are not sure whether a change counts as chart sensitive, ask before making it.
How to request a change
Every campaign runs a shared thread with your EVEN team. Flag what you need there. Merch stock is the exception that needs no request at all: inventory syncs in real time against your store of record, so what your store says is what the site sells, and oversell cannot happen.
Orders already in flight
Orders keep moving while you make changes. Statuses and tracking are updated in the merch dashboard throughout the campaign, and what your team updates is what the fan sees in their account.
Deciding what to change
The dashboard is real time, so you are not changing things blind. Sales and revenue, traffic sources and conversion, fan growth, opt in rates, and geography all update live, and that is usually what tells you a price, a product, or a module needs to move.