About 90 % of all trains that you can take require no reservation. If you avoid Portugal, Spain and to some extent France you will be fine without reservations most of the time. Travelling without reservations will in some countries take longer time as you need to travel with regional trains instead of high speed trains.

What countries are you planning to visit?

So I will be visiting, Spain, France, Italy, Switzerland, Germany, Czech Republic, Netherlands. 
 

do you think it would it be a better idea to travel via high speed trains and pay the reservations costs or would it be cheaper to pay for all my trains individually via trainline? When looking on train for the individual costs of going between each place seemed to come out cheaper on comparison. 

It depends how flexibile you wanna be The pass is the best mix of flexibility and money saveing. 

Booking individual in advance so called “Advanced” “Saver” or “Promo” fares are the cheapeast but often bounded to a specific train on a specific day with often reduced or non possibility to refund or exchange.

Finally the booking on the spot this ofcourse the most flexible route but even the most expensive. 

What is finally better for depends on your preference of flexibilty and your Route. Nobody can do the maths for you as we dont know where you wanna go when and what you wanna do. (e.g. a continous Interrailpass can be good if you set “bases” and have daytrips from there like Berlin to Potsdam, Venice to Verona,Padova,Trieste).

The bad reviews on several pages is often because people doesnt read before they buy and notice then that 90% of their Routes are on Reservation compulsory trains. (and doesnt use the slower reservation free trains) 

The most unfriendliest Countries are Spain (as they make it very difficult to get reservations for Railpassuser in advance) and France (especially with International Highspeed services like TGV to Spain, Switzerland,Germany,Belgium,Italy as they charge sometimes up to 56€ just for a seat , or Eurostar between London and Lille,Brussels,Rotterdam,Amsterdam,Paris) 
Ontop of that a lot of these International Highspeedtrains from/to France have just limited seats for Railpass holder :/ 

Italy is doable (Highspeed trains need a reservation of 10€ per seat/train, Intercity (Fasttrains) can be reserved for 3€ and often you even have regionaltrains that a reservation free but take longer ) 
Switzerland,Germany,Czech Republic & Netherlands are on the top site for Pass ussage as train travel is quite expensive when booking individual tickets (Especially Germany & Switzerland) and most trains are not reservation compulsory. (You  often still have the possibilty to reserve a seat for 3€ - 8€ ) 

All in all its really not that much different as what BritRail in GB offers, except that as seewulf explains some countries have a far higher % of RES-mandatory trains-for the big most parts these are these new hi-speed lines, as such understandable, as they do not take standees. To the extreme utter surprise of many: yes, if trains are really full one can also travel standing-again very much as in GB. There will be more stops where people get off and on etc.

Best site for general intro: seat61.com

Smarter people but still a bit unsure set their route more to how easy it is to organise travel-and forfeit for this time the hard ones. A real PITA in general-to please those Brits from the islands in the NorthSea, is this €*. That may mean some re-thinking. And 8 count in 1 MO means about 3-4-d/each-forget that ESpana, as you have to come back moreorless sameway as going. OR-an insult for some, I am very well aware-use some smartly and well planned flite of a lowo costo to bridge some longer distance.