2012 Ford Focus 1.6Ti-VCT Titanium Best Oil + Service Parts

Hi all. 

Just seeking out advice really on the following:-
- 2012 Ford Focus 1.6Ti-VCT (125PS). 

I am considering installing a Green Cotton Performance air filter. 
The cylindrical shaped air filter comes back to me with a green tick when I enter details and specifications on sites - stating the rounded filter will fit.

Is this correct or do I require the flat, more rectangular / box shape filter? 
I ask due to having conflicting results come back on different sites. 

Also any recommendations for air filters is appreciated. 

The car would benefit from a service which I intend to carry out - or I at least want to purchase the parts required so I can potentially take it to be serviced with a knowledge of what items and parts are going into the engine. 

My questions and enquiries in to this are more so regarding the oil and spark plugs. 

When I search for the best / optimum oil for the model year and specs it brings me to a web page informing me that the original / factory oil is Millers Trident Professional ECO 5w30 Fully Synthetic. 

Would the full service kit in this regard be worth opting for as it comes supplied with:- 
 
- Bosch oil filter x 1 
- Bosch carbon anti odor cabin / pollon filter x 1 
- Seal for oil sump drain plug 
- Miller's Oils Trident Professional ECO 5w30 Engine Oil 5 Litres 

Would this be the best option or is it worth shopping around and individually purchasing parts? 

I've had the following results come back to me when searching the best oil:-
- Castrol Magnatec 
- Mobil Super 3000 
- Shell Helix 
- Triple QX 

Would any of these be as good - or potentially 'better' than the original Millers?

Is there any particular recommended spark plugs? 

I read that Denso are highly regarded but also aware other manufacturers are rated quite high too. 
Also should I be looking at iridium tipped or any other specs or particulars? 

I appreciate all help, any details and thanks in advance. 

Focused87