DescribeSObjectResult: Check whether the object is Custom or Standard

List<String> allCustomObjsList = new List<string>();
List<String> allStandardObjsList = new List<string>();

for(Schema.SobjectType obj : Schema.getGlobalDescribe().values()) {
    Schema.DescribeSobjectResult objResult = obj.getDescribe();
    if(objResult.isCustom()) {
        String strObjName =objResult.getname();
        allCustomObjsList.add(strObjName);
    }
    else {
        String strObjName =objResult.getname();
        allStandardObjsList.add(strObjName);
    }
}

System.debug('Custom Objects List: ' +allCustomObjsList);
System.debug('Standard Objects List: ' +allStandardObjsList);

If you need to check for a specific object, execute the below code:

Schema.DescribeSObjectResult describeAccount = Schema.sObjectType.Account;
System.debug(describeAccount.isCustom());

Similarly you can use other methods for describing sObjects, the list of which can be found below:
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_sobject_describe.htm

Fetch recordType Name and recordTypeId without SOQL

To avoid SOQL Limit we can use dynamic apex to get RecordTypeId. We can get a particular RecordTypeId of a particular sObject or get all recordTypeid of one sobejct in a map.

global class RecordTypeUtils {
    
    //Method to get the recordTypeId 
    public static Id recordTypeId(string obj,string recName){
        Id recTypeId;
        if(obj!= null && recName != null){
            recTypeId= Schema.getGlobalDescribe().get(obj).getDescribe().getRecordTypeInfosByName().get(recName).getRecordTypeId();
        }  
        return recTypeId;  
    }
    
    //Method to get the map of recordType Name as key and recordTypeId as value 
    public static Map<String,Id> recordTypeMap(string obj){
        Map<String,Id> recTypeNameWithIdMap=new Map<String,Id>();
        if(obj!= null){
            for(Schema.RecordTypeInfo recInfo : Schema.getGlobalDescribe().get(obj).getDescribe().getRecordTypeInfosByName().values()){
                recTypeNameWithIdMap.put(recInfo.getName(),recInfo.getRecordTypeId());
            }
        }
        return recTypeNameWithIdMap;
    } 
}

I created a record type "NewLabel" on Account object. Enter the below Apex code in Execute Anonymous window and check the output:

Map<String,Id> recTypeIdMap=RecordTypeUtils.recordTypeMap('Account');
System.debug(recTypeIdMap);
Id recId=RecordTypeUtils.recordTypeId('Account','NewLabel');
System.debug(recId);

Id recordTypeId = Schema.SObjectType.Account.getRecordTypeInfosByName().get('NewLabel').getRecordTypeId(); 
System.debug(recordTypeId);

Note that values of recId and recordTypeId in your output is same.

Check the link below to check a utility class that performs the query against the RecordType object
https://interactiveties.com/blog/2016/recordtype-utility-class.php

Apex: Get sObject details using ID

Id id = 'a0M7F000000qXgg';
Schema.sObjectType objType = id.getSObjectType();
Schema.DescribeSObjectResult objDescribe = objType.getDescribe();

System.debug(objDescribe.getName());

Similarly, you can get other sObject details using the methods described in the link below:
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_sobject_describe.htm

Dynamic SOQL and SOSL

To create a dynamic SOQL query at run time, use the database query method. Check the reference link for more details.

List<sObject> sobjList = Database.query(string);

To create a dynamic SOSL query at run time, use the search query method. For example:

String searchquery = 'FIND \'Edge*\' IN ALL FIELDS RETURNING Account(Id, Name), Contact, Lead';
List<List<SObject>>searchList = search.query(searchquery);

To prevent SOSL injection, use the escapeSingleQuotes method. This method adds the escape character (\) to all single quotation marks in a string that is passed in from a user. The method ensures that all single quotation marks are treated as enclosing strings, instead of database commands.

fieldList = (fieldList!=null) ? String.escapeSingleQuotes(fieldList) : fieldList;

References:
http://metillium.com/2016/03/variable-binding-in-dynamic-soql/

Salesforce Custom Settings

Custom settings are similar to custom objects and enable application developers to create custom sets of data, as well as create and associate custom data for an organization, profile, or specific user. Custom Settings data is stored in the application cache, which enables efficient access without the cost of multiple repeated queries to the database. As long as you query the Custom Settings using GET methods rather than an SOQL query you can retrieve all of the values with literally zero impact on the governor’s count of the number of queries performed or rows retrieved.

List Custom Settings

It provides a reusable set of static data that can be accessed across your organization. Data in list settings does not vary with profile or user, but is available organization-wide.

The following are instance methods for list custom settings.

• getAll(): Returns a map of the data sets defined for the custom setting.
• getInstance(dataSetName) / getValues(dataSetName): Returns the custom setting data set record for the specified data set name.

Hierarchy Custom Settings

It uses a built-in hierarchical logic that lets you "personalize" settings for specific profiles or users. The hierarchy logic checks the organization, profile, and user settings for the current user and returns the most specific value. In the hierarchy, settings for an organization are overridden by profile settings, which, in turn, are overridden by user settings.

References:
http://www.brcline.com/blog/salesforce-custom-settings
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_custom_settings.htm