Summarizing where i am..
Approach 1, I accepted i have to make now 10 calls to Browse API for what i used to do with 1 single call to findingAPI. One call per each marketplace supporting Browse API. And later you have to loop all the results to don't produce duplicate outputs, since same product can be available in several marketplaces. The amount of process required to get same (~) results than before, is in a * 11 range.
In addition, client Auth flow, forces a new token every 2700 seconds, so even if you are just going to use summary_items search, may want to use the User Auth flow in order to get an interesting expiry date for your token.
New problems i found since then.
- The affiliate links are returned for the marketplace you are searching, so i need to replace ebay domain in the link, as well as rotation id.
There is no way to get this links converted to the country you are using at deliveryCountry filter.
- And the same happens with prices and shipping costs, no way to get currencies converted to a delivery destination, because they are provided in base to the marketplace you search, X-EBAY-C-MARKETPLACE-ID header. contextualLocation doesn't change anything of this.
Approach 2, Instead of query all marketplaces with a fixed deliveryCountry filter, you can query in the marketplace you want the links and prices for, changing the itemLocationCountry filter.. but.. how many queries can become this ?? It will give you correct affiliate links and prices in the right currency.. but.. maybe to get an approach to current global worldwide search in Finding API, we are speaking about run 20-50 API queries changing itemLocationCountry to major countries selling in Ebay ? and most of the times to get nothing.. just to be sure you are not missing anything.
So what to do.. approach 2 looks like the correct one.. so trying to figure out which list of countries use for the query.. for sure all of those with a marketplace associated, plus China and Japan.. Ukraine and Russia.. and some more European countries.. so maybe around 20 API calls for what used to be 1 single call to finding API.
the interesting, as per experiments using itemLocationCountry is that data is available on the X-EBAY-C-MARKETPLACE-IDs , just any filter in the API make it available in a single query.