All settings concerning the Computer affects only the computer as player and not the assistance feature.
The algorithm generates a list of possible and valid words on search. This list is sorted by the value of a word and therefore the best word has the first index. With limitation of performance the order of word is controlled depending on the option deterministic. If this option is checked the word with a value next to given percentage of best word is used. If, for example, the best word results in 22 points and the second best in 16, a limitation of performance by 95% means the target value is with 22*0.95 about 21. Hence the best word is still placed since it's value is closer to the target value. With 75%, target value would be about 16 and the second best word will be placed. High values above 90% makes sense for extensive dictionaries. The post-hoc calculated game result at the game course corresponds approximately to the adjusted performance. If performance will be limited non-determined, each entry of the sorted list is moved with given probability to the end of the list. The post-hoc game result does not correspond to the adjusted value. In a figurative sense, deterministic limits the points and non-deterministic affects the vocabulary.
Basically, performance limits the result only for moves that computer player makes for itself. It neither applies to the post-hoc analysis nor the assistance - it that cases the best word will be shown always.
With trust in challenge mode you let the computer object words that humans play in the challenge mode. This option simulates a normal game play by checking placed words disregarding the fact that the computer is allmighty because it 'knows' if a word is valid or not. A value of 100% means non of your words will be checked, and 50% that in average every second word will get challenged.
Parallel processing accelerates calculation of moves significantly, if checked. The option is available for multi core CPUs only. Disadvantage could be that feedback is given rarely and input is blocked sometimes. Additionally, the programming is rather complex and errors may occur. By deactivating the option a sequential (but slow) processing will be performed.
If show computer's tiles is checked, pieces of the computer player are shown during search. If not, the own tiles on the rack are still visible. Additionally, this options is used to show the exchanged letters at the game course or to replace them by wildcards until the game has been finsihed.
If the computer finds no valid words, or if the criteria to place a word, like minimum value, are not met, the option complete exchange instructs the computer to exchange all letters except the one with the highest value, and jokers. If this option is deactivated, the computer will exchange multiple tiles first or, if all tiles are available only once, the one with the highest value.